Thanks, I understand your point.
Unfortunately making Nabble installable on a server wouldn't help, the problem is sharing users among different platforms.
One of your competitors is using rpx (
https://rpxnow.com) that simplifies the management of users and password (i think up to the point that it elinates the need of storing userid/password). I think you might find it useful.
I'm currently using spruz (which uses rpxnow too) to create a social network and I was hoping to replace their forums with Nabble (that is way better). Too bad I'll have to wait.
I'll continue checking Nabble from time to time, I really think it's a powerful piece of software!
Remo.D