It's also ... not an awful lot like CS at the moment. Mostly the size and complexity of the map.
for audio/visuals the game is currently pretty basic because I am not wearing all the game development hats, and 3D graphics/audio/animation is not my favorite things (but PR queue is open if anybody is interested), but it can be scaled to more complex map, I actually convert old "real" dust2 map to this game a _year_ ago and record video of playing it https://www.youtube.com/watch?v=aIBVGZanVvU
Can't see how that trade mark could stand against a challenge (in UK/EU)?
See eg Art.4, Art.7(1)(c) of EUTMR.
IANAL, these are my personal opinions and unrelated to my employment.
I am also not a lawyer, but I would not like to step into a trademark dispute just because it 'seems perfectly fine'.
Albeit in this case you're most likely to just get a cease and desist rather than getting sued.