If you give me your Sourceforge user ID, I can set you up with commit access to the VuFind repository so you can establish a branch. Alternatively, if you want to maintain your repository locally, using a vendor branching strategy is a good way to keep your modifications in sync with the latest trunk – that’s what I do for Villanova’s various VuFind instances. This has the advantage of allowing me to keep all of my configuration details in SVN without exposing any sensitive details (like passwords) to the world through Sourceforge. I can elaborate on how this works if you’re not already familiar with the technique (there are also some details in the wiki here: http://vufind.org/wiki/subversion#vendor_branching).
In any case, we’re always happy to receive shared code! Are there any particular features you were thinking of sharing? If so, it might be worth opening up some JIRA tickets to track them – that’s a good place to share patches for comment, and it’s nice to have new features on the radar so other institutions don’t repeat work that has already been completed.
Good luck with the upgrade, and please let me know if there’s anything else I can do to help out with the process – I’m always happy to answer questions about the code if they arise.