In order to make Weka more accessible for people that like having access to the latest code, we have been looking into ways of bringing Weka to Github. Especially, since our faculty already has an organizational account there.
However, Weka was original stored in a CVS repository and then got migrated to Subversion. Not only has it a lot of branches, not all of them are publicly available, like commercial ones. This all complicated the migration to Github.
In the end, we decided to simply use Github as a mirror of our inhouse Subversion repository. With that, you can at least clone and fork in the usual Github fashion. The only downside is, that you can't make any pull-requests, being downstream. For fixes/additions, you still need to send in a patch file to the Weka mailing list.
Long story short, we now have two repositories, one for developer version (trunk or HEAD) and one for the stable 3.8 branch: