Full SPDX-ication

CONTRIBUTING.md

@@ -20,14 +20,26 @@ Now for the mechanics of the process, and some do's and don't's.
 
 This is highly important - this list *only* contains freedom-respecting things!
 If you are sending a pull request linking to code, ensure it is licensed under a
-[freedom-respecting license][1].
+freedom-respecting license. This includes, but is not limited to:
+
+- Anything on the [OSI license list][1]
+- Creative Commons Zero
+
+If you're not sure, better to ask first. If it's not on the list above
+especially.
 
 ### Indicate the license for anything you add clearly ###
 
-Ensure that you use the correct name for the license (as per [this][1]), and
-indicate any further restrictions clearly. Also check if the license is in use
+Ensure that you label licenses correctly. ``awesome-c`` now uses [SPDX][2]
+license labels, so please use those. If the license is weird or not on the list,
+label it as clearly as possible. Also check if the license is in use
 already - if it is, don't create another link to it.
 
+Sometimes, libraries or frameworks will contain documentation or code under
+different licenses to the library itself (such as tests or examples). There is
+no need to indicate their licenses in that case. However, if the program itself
+is what is being put on the list, *obviously* its license matters.
+
 ## Maintain alphabetical order within sections ##
 
 Pretty self-explanatory, really. Numbers are considered to be higher-ordered
@@ -39,5 +51,5 @@ The commit message should state clearly *what* you did (adding, removing,
 clarifying, etc.), with *what* (usually by giving the name of the entry), in the
 present continuous tense (i.e. 'adding' not 'added').
 
-[1]: https://www.gnu.org/licenses/license-list.html
-[2]: http://freedomdefined.org/Licenses
+[1]: https://opensource.org/licenses 
+[2]: https://spdx.org/licenses/