If the present project is having a tough time doing enhancements, I should think it mighty questionable to try to draw it into core, that presses it towards a group of already very busy developers.
On the other hand, if the present development efforts can be made more public, by having them take place in a more public repository, that at least has potential to let others in the community see and participate. There are no guarantees, but privacy is liable to hurt. I wouldn't expect any sudden huge influx of developers, but a steady visible stream of development effort would be mighty useful to a "merge into core" argument. A *lot* of projects are a lot like this. On the Slony project, we have tried hard to maintain this sort of visibility. Steve Singer, Jan Wieck and I do our individual efforts on git repos visible at GitHub to ensure ongoing efforts aren't invisible inside a corporate repo. It hasn't led to any massive of extra developers, but I am always grateful to see Peter Eisentraut's bug reports.
