Okay, I am curently visiting my parents and have therefore been unable to test it, but a free fan-game set in the B5 universe can be downloaded from here. I can't tell if it is good, but they claim on their homepage that the game has the following features:
• original, state-of-the-art rendering engine capturing the atmosphere of the epic universe
• over a dozen ships and space structures from the show
• groundbreaking, intriguing and extremely detailed prologue storyline
• explore different locations including asteroid belts, hyperspace and more
• ultimate space combat game utilizing plasma and even more dangerous weapons for total destruction
I hope you enjoy it, and let us know what you think of it.