Concurrent multi-user support has been part of our long-term goals for a while now:
Time to update the status of this feature request…
Note it still says “long-term”, which currently means several years ahead of us.N'uno commented
It isn't useful for just some users. It is vital for most small businesses, and mine is no exception. Multi-user support would also benefit many home users. I understand your code base is overly complex, mixing c, scheme, emulated oop and c++. It doesn't follow nowadays' best practices too. I guess a complete rewrite is highly recommended, though painful. But I'm sure there would be plenty of community support to feed a rewriting fork, and there are plenty of frameworks that can easily solve those dependencies and give it true cross-platform capabilities, allowing us to focus on the functionalities rather than system/lib/GUI stuff. I have a strong background on every languages GnuCash uses today, but I'd prefer to use a RAD environment. The Lazarus project (www.lazarus-ide.org) is one of those things, for example. Using Free Pascal, an object pascal derivative, you could cut that long functional catch up phase to a couple of months, and the resulting GnuCash would be much more powerful.
Anyway, I'm not GnuCash's mentor, but I do love it and would like to see it evolve. My time is really scarse, but I'd love to help too! :)