Yes, this is the requirement of the funder, not our own requirement. Collaboration formally with the containing University could potentially be a possibility.
Trouble with university funding depts is that they're usually slow, although my University isn't too bad: at least they let their Researchers take on outside contracts like this & I believe will handle all the paperwork / legals for a small cut. I'll forward your link round the department. Someone might bite...
We're almost there with the open-sourcing, I'm pleased to say.
Sadly this process has taken far longer than we hoped because the codebase, which was started about 6 years ago and which was not started with open-sourcing in mind, ended up with a lot of things like embedded passwords, deploy scripts, people's names, API keys, etc. There's been a mammoth effort to deal with that. The entire deployment system has had to be rewritten, for instance, and that done while trying to keep a very busy production system running that also hosts a pile of third-party sites without downtime.