Well our board has only 550 members and these seem to be all that ever were on it, maybe someone of the cabinet can tell some numbers but really active are surely less than 100 and of these a lot are running not only this club but other clubs too.
And as we play almost exclusively the Tiller Civil War games it also limits the pool of people than join us.
I'm sure there is a bunch out there play boardgames via the VASSAL system, others play CW mods for modern games like the Total War series, again others may only play some grand strategy games like the CW series of AGEOD, the pool of people playing CW related stuff is surely large but only a small portion ends up here.
You should really go to other boards too, be it game related like
http://www.wargamer.com/ or historic related like
http://civilwartalk.com/ or maybe even professional boards for graphics and whatever else you need.
Regarding BaB, well I thought about buying it but some rather strange game mecanics kept me from it like the way FoW works for example. It's seem a good engine but it needs to be developed beyond the current status or it is just a nice attempt but nothing more. There is still a bunch of active BaB players but the problem is if nothing goes ahead from the design perspective the players get the usual feeling of gaming a dead game, the natural effect is that it's less and less played. There also seem to have been PBEM issues what is absolutely fatal for such a game, the last patch from July 2015 so fixes seem to be overdue what just proves that it was likely dropped by the designer/publisher, at that point it makes no sense to beat a dead horse neither for the owner nor for the rider.
So the failure of BaB shouldn't discourage you, it is just an example of what to avoid.
_________________
Lieutenant General Christian Hecht
Commander I Corps, Army of the Potomac
"Where to stop? I don't know. At Hell, I expect."