spamguy
Create a credits/license page
Credit people who contributed code, icons, and ideas. Supply relevant licenses. Individual maps should not be credited here. Variant credits should be accessible from the new game section.
- Icons: freepik
Read here about the implications of not having a license:
https://help.github.com/articles/open-source-licensing/
Additionally, you should create a contributor agreement, the specifics of which may vary with the intent of your licence. Since you're not likely to seek legal advice, I'll help you put together something that'll probably be better than nothing in the interest of you being able to accept contributions and still be able to make changes to the licence later.
MIT license added to source code. Still needs an explicit page on the site.