Clarify licensing

Fixes: #1188

README.rst

@@ -41,6 +41,21 @@ Contributing
 
 Please read `Contribution guidelines`_ if you wish to contribute.
 
+Licensing
+=========
+
+The code in the ansible-lint repository is licensed under the MIT license. If
+you contribute to this repository, that license applies to your contributions.
+
+The ansible-lint project also imports the Ansible python module, which is
+licensed under the GPLv3+ license. Because of this import, the GPLv3+ rules
+apply to the full distribution of ansible-lint. We maintain the MIT license on
+the repository  so we can fully use an MIT license in the future if we ever
+remove the runtime dependency on Ansible code.
+
+Installing the `ansible-lint` python package does not install any GPL
+dependencies, all of them are listed as extras.
+
 Authors
 =======
 

setup.cfg

@@ -32,6 +32,7 @@ classifiers =
   Operating System :: OS Independent
 
   License :: OSI Approved :: MIT License
+  License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
 
   Programming Language :: Python
   Programming Language :: Python :: 3
@@ -88,16 +89,16 @@ console_scripts =
 
 # core will point to ansible-core>=2.11 as soon that is released
 community =
-  ansible>=2.10
+  ansible>=2.10  # GPLv3+
 # this will move to latest stable ansible as soon that is released
 core =
-  ansible-base>=2.10
+  ansible-base>=2.10  # GPLv3+
 # will install ansible from devel branch, may break at any moment.
 devel =
-  ansible-core @ git+https://github.com/ansible/ansible.git
+  ansible-core @ git+https://github.com/ansible/ansible.git  # GPLv3+
 # yamllint must remain optional
 yamllint =
-  yamllint >= 1.25.0  # GPL
+  yamllint >= 1.25.0  # GPLv3
 
 [options.packages.find]
 where = lib