diff --git a/check/check.go b/check/check.go
index 5bf557817..182b47835 100644
--- a/check/check.go
+++ b/check/check.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package check runs checks on a project.
 package check
 
diff --git a/check/checkconfigurations/checkconfigurations.go b/check/checkconfigurations/checkconfigurations.go
index cded58f71..c44a74f95 100644
--- a/check/checkconfigurations/checkconfigurations.go
+++ b/check/checkconfigurations/checkconfigurations.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 /*
 Package checkconfigurations defines the configuration of each check:
 - metadata
diff --git a/check/checkdata/checkdata.go b/check/checkdata/checkdata.go
index aaee70a9a..0183d03bf 100644
--- a/check/checkdata/checkdata.go
+++ b/check/checkdata/checkdata.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 /*
 Package checkdata handles the collection of data specific to a project before running the checks on it.
 This is for data required by multiple checks.
diff --git a/check/checkdata/library.go b/check/checkdata/library.go
index 361b847e3..5dc4682c7 100644
--- a/check/checkdata/library.go
+++ b/check/checkdata/library.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 package checkdata
 
 import (
diff --git a/check/checkdata/schema/schema.go b/check/checkdata/schema/schema.go
index eb3d9c2dd..42cd82cac 100644
--- a/check/checkdata/schema/schema.go
+++ b/check/checkdata/schema/schema.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package schema contains code for working with JSON schema.
 package schema
 
diff --git a/check/checkfunctions/checkfunctions.go b/check/checkfunctions/checkfunctions.go
index 42f4e2cd7..a12665fe4 100644
--- a/check/checkfunctions/checkfunctions.go
+++ b/check/checkfunctions/checkfunctions.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package checkfunctions contains the functions that implement each check.
 package checkfunctions
 
diff --git a/check/checkfunctions/library.go b/check/checkfunctions/library.go
index da59fa2cf..7a3236a50 100644
--- a/check/checkfunctions/library.go
+++ b/check/checkfunctions/library.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 package checkfunctions
 
 // The check functions for libraries.
diff --git a/check/checkfunctions/sketch.go b/check/checkfunctions/sketch.go
index 741becc43..73a3133d5 100644
--- a/check/checkfunctions/sketch.go
+++ b/check/checkfunctions/sketch.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 package checkfunctions
 
 // The check functions for sketches.
diff --git a/check/checklevel/checklevel.go b/check/checklevel/checklevel.go
index 8510d13fa..5f79d59c6 100644
--- a/check/checklevel/checklevel.go
+++ b/check/checklevel/checklevel.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package checklevel defines the level assigned to a check failure.
 package checklevel
 
diff --git a/check/checkresult/checkresult.go b/check/checkresult/checkresult.go
index e63f80759..437014745 100644
--- a/check/checkresult/checkresult.go
+++ b/check/checkresult/checkresult.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package checkresult defines the possible result values returned by a check.
 package checkresult
 
diff --git a/configuration/checkmode/checkmode.go b/configuration/checkmode/checkmode.go
index 120384b20..194ca5bd3 100644
--- a/configuration/checkmode/checkmode.go
+++ b/configuration/checkmode/checkmode.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package checkmode defines the tool configuration options that affect checks.
 package checkmode
 
diff --git a/configuration/configuration.go b/configuration/configuration.go
index b61bbe931..90e8c6c00 100644
--- a/configuration/configuration.go
+++ b/configuration/configuration.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package configuration handles the configuration of the arduino-check tool.
 package configuration
 
diff --git a/configuration/defaults.go b/configuration/defaults.go
index b17dc3f37..618979014 100644
--- a/configuration/defaults.go
+++ b/configuration/defaults.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 package configuration
 
 // The default configuration settings.
diff --git a/main.go b/main.go
index 53101788e..2034ce47d 100644
--- a/main.go
+++ b/main.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 package main
 
 import (
diff --git a/project/library/library.go b/project/library/library.go
index e6d4bf75a..6cb4efe96 100644
--- a/project/library/library.go
+++ b/project/library/library.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package library provides functions specific to checking Arduino libraries.
 package library
 
diff --git a/project/library/libraryproperties/libraryproperties.go b/project/library/libraryproperties/libraryproperties.go
index 024b6f6da..d89c5e7ff 100644
--- a/project/library/libraryproperties/libraryproperties.go
+++ b/project/library/libraryproperties/libraryproperties.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package libraryproperties provides functions for working with the library.properties Arduino library metadata file.
 package libraryproperties
 
diff --git a/project/packageindex/packageindex.go b/project/packageindex/packageindex.go
index d2005b90b..4cc5da8bc 100644
--- a/project/packageindex/packageindex.go
+++ b/project/packageindex/packageindex.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 /*
 Package packageindex provides functions specific to checking the package index files of the Arduino Boards Manager.
 See: https://arduino.github.io/arduino-cli/latest/package_index_json-specification
diff --git a/project/platform/platform.go b/project/platform/platform.go
index a6534ad9f..462c62266 100644
--- a/project/platform/platform.go
+++ b/project/platform/platform.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 /*
 Package packageindex provides functions specific to checking Arduino boards platforms.
 See: https://arduino.github.io/arduino-cli/latest/platform-specification/
diff --git a/project/project.go b/project/project.go
index 5c4a7a112..4a70343df 100644
--- a/project/project.go
+++ b/project/project.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package project finds and classifies Arduino projects.
 package project
 
diff --git a/project/projecttype/projecttype.go b/project/projecttype/projecttype.go
index 96f300358..f4548abca 100644
--- a/project/projecttype/projecttype.go
+++ b/project/projecttype/projecttype.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package projecttype defines the Arduino project types.
 package projecttype
 
diff --git a/project/sketch/sketch.go b/project/sketch/sketch.go
index af05a809f..b833d6e24 100644
--- a/project/sketch/sketch.go
+++ b/project/sketch/sketch.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 /*
 Package sketch provides functions specific to checking Arduino sketches.
 See: https://arduino.github.io/arduino-cli/latest/sketch-specification/
diff --git a/result/feedback/feedback.go b/result/feedback/feedback.go
index 655fc5418..e43258a1c 100644
--- a/result/feedback/feedback.go
+++ b/result/feedback/feedback.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package feedback provides feedback to the user.
 package feedback
 
diff --git a/result/outputformat/outputformat.go b/result/outputformat/outputformat.go
index ca8cbe9ff..9b7c39249 100644
--- a/result/outputformat/outputformat.go
+++ b/result/outputformat/outputformat.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package projecttype defines the output formats
 package outputformat
 
diff --git a/result/result.go b/result/result.go
index 54d5a0ead..ec4e377ea 100644
--- a/result/result.go
+++ b/result/result.go
@@ -1,3 +1,18 @@
+// This file is part of arduino-check.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
 // Package result records check results and provides reports and summary text on those results.
 package result