"Download a copy of Gamut, our client software, to enter the world of Volity gaming."

They're also developing a web-based version: http://www.volity.org/wiki/index.cgi?Web_Client

Anyway, you should probably have something more to distinguish yourself besides just being online-only. The Volity system is actually pretty interesting; it works over Jabber.

There are a ton of sites in the multi-player gaming niche. I think there's still lots of room for competition, and many ways to compete with existing sites. Whether on game selection / implementation or technology improvements.

They can still use Java and let users launch the application via Java Web Start.