I wish it were at github :-)
Ah well, I'll consider that. Now that I've started working on the wiki, the difference in wiki engines might make a transition more difficult. BitBucket uses Creole, unlike GitHub. But then again, it might be better to have all the docs & guides on a separate site (on OpenShift perhaps), just like Arquillian - http://arqpreview-alrubinger.rhcloud.com/
I'll start by saying that it doesn't matter to me where it's hosted. It took me no more time to check it out and start playing with it then if it were on github. It's DVCS, that's the important part. So I'd say choose what you think is best for you.
For completeness, the Github wiki does support Creole. In fact, it supports every major lightweight markup language thanks to the github-markup and github-gollum template abstraction libraries (markup is the library, gollum is the editor). You just select your markup in the menu above the upper right hand corner of the text area when you are editing.
I agree, though, that the guides should be hosted on a separate site to bring them all together. That's a problem we haven't yet completely solved...but that shouldn't get in the way of writing up the tutorials. Moving information around is far easier than writing it
Btw, the wiki is looking good!!! I can't wait to dive into it! For the audience, here's the link:
My initial statement needs to be updated, you do have a tutorial in progress. So it's us that could contribute to your effort
Here's an example of the Creole markup in a Github wiki page (a gist and a repo wiki use the same editor):
Note that Github does not support syntax highlighting in any markup language other than Markdown. There's an open ticket for that.