As of yesterday, Vienna development happens over at GitHub. All our Subversion commit history going back to 2005 was migrated into a new Git repository. The trunk will now always contain the version currently being worked on. Source for all previous releases will be available as separate tags (2.0.0 to 2.6.0).
To get the latest source, simply paste the following into a shell prompt:
git clone email@example.com:ViennaRSS/vienna-rss.git
To do this, you will need an up-to-date version of the Git version control system. I recommend installing it via homebrew, an awesome package manager for Mac OS X. Alternatively, you can use GitHub’s freely available GUI client: GitHub for Mac. The latter will also optionally install the command line tools for you.
Have fun :-)