When you join a project on WMD and become a Team Member, not only do you get to see it being made, play regular new versions of it, and speak to the devs directly, but you also get rewarded for doing so.
These rewards are known as Project Perks and different ones get activated depending on the Tool Pack you currently own.
Check out the C.A.R.S. specific Perks over here! and if you see one you like simply upgrade!