Eeek, I'm sorry, I missed this at first.
Currently the only way we can allow multiple authors on a project is if they are FAs. If you are using the SVN here, the owner of the project can allow more than one person permissions to submit to the SVN and push versions. Also, depending on who it is/what project, if I know the people involved well enough, I'm willing to bounce ownership back and forth between them since I know they are "legit" on that project. So, just drop me a PM and, depending on what project it is, I can give you ownership for now and pass it back to the other person later. A little convoluted I know, but not too bad, and not really a big deal on my end to do it, only takes me a couple minutes to do it.