If the deck format is some kind of text like XML you could look into using git for distribution and a simple text editor for editing.
Exactly the right avenue. Unfortunately, Anki typically uses its own idiosyncratic data format that's not very handy for this kind of thing, but it's possible to export and import decks to text, as it turns out.
The issue with this is that if you're months into studying a deck and you'd like to merge edits from other contributors, I'm not certain that you simultaneously import the edits and keep all of your progress.
Even so, the text deck route has the most promise as far as I can tell.
You know the drill - If it's worth saying, but not worth its own post (even in Discussion), then it goes here.