While unlikely for an individual user, companies have been sued for using unlicensed plugins. The BSA (Business Software Alliance) offers rewards for whistleblowers. Your "best free key" could cost your employer $50,000.
The "best" SubD SketchUp license key is a purchased directly from the developer or the Extension Warehouse. It provides the peace of mind, stability, and professional support required for high-level 3D modeling. subd sketchup license key best