The Earth Alliance funded the first few attempts exclusively; after
they'd dumped all their money into B4, they needed outside funding to get B5
going, and the Minbari were first to contribute money as a show of good faith.
Then the Centauri added additional funding. Those are the only two other
races that've contributed significantly.
The world B5 orbits is Epsilon 3.
PPG = Phased Plasma Gun.