Peers code, markup, and style files have the AGPLv3+ license.
You can find a copy of the license here: https://www.gnu.org/licenses/agpl.txt
Peers media files and plain textual information contained in the markup have the CC BY-SA 4.0 license.
Official legal version:
https://creativecommons.org/licenses/by-sa/4.0/legalcode
Human readable interpretation version:
https://creativecommons.org/licenses/by-sa/4.0/
Please note that each of the projects that Peers links to has their own license and policies.