chore: Dual license between Unlicense and MIT

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Features
 
+- **relicense:** Dual-license between MIT license and Unlicense ([#4870](https://github.com/ScoopInstaller/Scoop/issues/4870))
 - **install:** Allow downloading from private repositories ([#4254](https://github.com/ScoopInstaller/Scoop/issues/4243))
 
 ### Bug Fixes

LICENSE

@@ -1,3 +1,31 @@
+INFORMATION ABOUT THIS PROJECT'S LICENSE (SHORT)
+============================================================================================
+This project is licensed under the Unlicense or the MIT license,
+at your option.
+
+INFORMATION ABOUT THIS PROJECT'S LICENSE (LONG)
+============================================================================================
+This project ("Scoop") is free software, licensed under the Unlicense or the
+MIT license, at your option. Scoop was previously licensed under only the Unlicense,
+but was dual-licensed later for several reasons.
+
+For more info, go to one of the following URLs:
+  - https://github.com/ScoopInstaller/Scoop/pull/4870
+  - https://github.com/github/choosealicense.com/issues/805
+  - https://github.com/ScoopInstaller/Scoop/issues/4868
+
+Scoop comes with ABSOLUTELY NO WARRANTY. Use it at your own risk. Scoop is provided
+on an AS-IS BASIS and it's contributors disclaim all warranties.
+
+You may use, modify, distribute, sell, copy, compile, sell, or merge Scoop
+by any means.
+
+Copies of both licenses can be found below.
+
+THE LICENSE OF SCOOP
+============================================================================================
+Unlicense
+---------
 This is free and unencumbered software released into the public domain.
 
 Anyone is free to copy, modify, publish, use, compile, sell, or
@@ -22,3 +50,28 @@ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
+
+MIT license
+-----------
+The MIT License (MIT)
+
+Copyright (c) 2013-2017 Luke Sampson (https://github.com/lukesampson)
+Copyright (c) 2013-present Scoop contributors (https://github.com/ScoopInstaller/Scoop/graphs/contributors)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.