GitHub is a wonderful service for programmers, but if you don't already know what it is, you probably don't want to join it just to use your GitHub account to log in to Mb2, but you can if you want.

Mb2 currently supports signing-on (and signing-up) via GitHub as a proof-of-concept for allowing logging in through social media. GitHub was chosen to be first because Mb2's user interface currently is "sub-optimal" (/me chuckles) and as such the next tranche to be exposed to Mb2 are likely to be people who can look beyond the surface, e.g., programmers.

If you sign-in via GitHub, your account's canonical name will be your GitHub account's name canonicalized. You can customize your nickname by putting the customization in the Nickname field of the sign-up and then clicking the Login with GitHub button. Your customization will only be accepted if it is compatible with your canonicalized name.

As an example of customization, if your GitHub account name is ctm and you put Ctm! in the Nickname field, then when you're logged in, your nickname will be Ctm!. If, however, you put deadhead in the Nickname field, then your nickname will simply be the unadorned ctm.

FWIW, GitHub hosts the source to this Player's Manual, this Player's Manual itself, Mb2's issue tracker and the source to mb2 (in a private repository).