which GPS receivers are supported? Trimble only?
It looks like any receiver which puts out GGA, GLL, RMC and/or VTG sentences can be used. I think Sam Wormley has a list somewhere of which receivers send what sentences.

is there a street/map database that comes along with this

It's not my project, but i would like to point out that that's a rather ambitious goal for a project currently at version 0.4 and not particularly old.