Starforce is an extremely notorious form of DRM. The product pages for Space Rangers 2, Space Rangers 2: Reboot, and Space Rangers Complete do not list it as being used. I am aware that the retail version of this game used that form of copy protection.
The original version had Starforce, the jewel case they released later didn't. Unless Stardock is getting sloppy, I didn't think the Impulse version had it.