You can clone with
HTTPS or Subversion.
See explanation in https://groups.google.com/forum/?fromgroups=#!topic/simple-build-tool/HReRqxmPE6Y
IMPORTANT This project has moved to https://github.com/sbt/sbt. This issue still exists to avoid dead links, but GitHub limitations prevent the original issue from being correctly preserved here. Please see sbt/sbt#550 for the full issue and to comment.