Maybe I will at some point, I don't currently have the time to work on another mod.

The old version of the mod is, however, still available from Paradox's site. It's one of the older files. You could use that to play with the multiple starbases, if you want.

The code is also visible on Github under the GPL, so you could, assuming you follow the license and know how to, publish your own version (please make sure not to use the "Outpost Slots" name, though.)
Do note that if you decide to do this, it would likely be incompatible with Outpost Slots.