A read-write mirror of Cayenne sources is published on GitHub:
Feel free to clone, fork, star Cayenne there. And of course submit pull requests.
Master Git Repository
“Master” writable repository is located here:
It is publicly readable, but only committers have write access.
Legacy Subversion Repository
Up to version 3.2M2 we used Subversion. For archival purposes SVN repository is still available
in a read-only mode:
Note that it contains branches and tags for releases prior to 3.0, that are not present in Git. So if you are looking for those older releases, you will have to use SVN.