Is there a way to give commit access to everyone on a public repository on GitHub? I want to use that repo as an alternative to GitHub Wiki.
If you're willing to invest some more work and resources into this, you can probably automate this with pull requests and the GitHub API.
I don't have the source code, but I know an example where someone did exactly this:
https://github.com/robashton/crowdsourcedhomepage
Quote from the readme:
Stick anything ( ͡° ͜ʖ ͡°) you like in here (make pull requests to the branch "gh-pages").
Every pull request will be automatically merged if possible, and then it'll end up on the home page of http://codeofrob.com
I didn't try it myself, but implementing something like this should be relatively simple:
At first glance, you just need a server/cronjob/whatever which uses the GitHub API to check your repo for new pull requests and to auto-merge each one.