We're planning to move our code repository away from SourceForge to GitHub. The current plan is to do the switch in the second half of August.
The full announcement can be found on the Mailing List.
If you are a MATSim developer with write-access to the current SVN repository, please have a detailed look at the announcement on the mailing list: You need to register on GitHub and tell us your username and public email-address, so we can correctly convert the svn repository to a git repository.
UPDATE July 27:
SourceForge is not able to fully restore our repository. We have a current backup, but instead of restoring this and then moving everything to GitHub a few weeks later, we will move directly to GitHub right now! See the announcement on the mailing list.
The half-way restored svn repository on SourceForge is now read-only and will remain like this. We will not enable write-access anymore to the repository on SourceForge! All future changes to MATSim will have to be done to the repository on GitHub we're currently setting up.