Yup, F.E.A.R. Combat is the same multiplayer portion that you get when you buy the full game, but it's free.
The cool thing is that you can play both owners of F.E.A.R. and F.E.A.R. Combat.
Personally, the only incentive I see in F.E.A.R. Combat is the free part. I'm not really a fan of F.E.A.R.'s deathmatch gameplay, it's WAY too fast. The weapons aren't that well balanced too. The G2A2 Assault Rifle way overpowered...just a burst kills you. But, I also like the physics and innovation in the weapons. The 10mm HV Penetrator is easily one of the most creative weapons ever. There just aren't many weapons that actually NAIL your opponents to a wall!
Either way, I can't wait to see this. I just hope Monolith realizes they should tweak the weapon power down a bit. It's just as ridiculous as the M6D Pistol in Halo: Combat Evolved.