The PS2 version of The Force Unleashed is single-player only. No split-screen, no co-op, no versus.
The PS2 port (by Krome Studios) was a ground-up rebuild with reduced scope. Multiplayer was cut to hit performance targets on weaker hardware. The PS2 version also lacks:
For the complete experience with multiplayer: Xbox 360 / PS3 / PC versions. The PS2 version is a distinct, lesser product.