For the renderer, Xara keeps theirs closed source; if they open sourced it, that would definitely be something we'd be interested in sharing. At LGM we talked about both projects switching to Cairo, which seems like a good approach. I don't know how Xara is doing with that, but Bulia has been experimenting with slotting Cairo in; we've been working with the Cairo folks as we discover issues, and they've been quite helpful at making our needs a priority.
The payed coders of xara since theire company is buyed from another one doesn't spend time working on the product. But it seems there are some coder that working on this and some xara dev's said they'll help out with commets on cdraw's (the closed source render lib) api.
Someone started a sf.net project but there isn't anything done yet: http://sourceforge.net/projects/free-libcdraw/
So if you feel interested you should contact the sf.net project admin.
If the projects produces working code its intended to be integrated in xara's svn. So 'Contributor Agreement' may need to be signed. But I'm not sure about this point!
Florian Ludwig