Is there some type of documentation for myBB?

Sure, we have a copy of the MyBB's docs, located at http://mybbsource.com/mybbdocs

How do I get my mods into the Mods Database?

To get your mod into our DB, your mod must meet two conditions:

1. It must be released exclusively at MyBBSource
2. The Website of the INFO function must be MyBBSource.com
   

If your mod meets these conditions, PM nickman. He will put you in the Contributers group, which will allow you access to our Mods DB.