If "free" is your main driver, OBDeleven’s basic OBD2 functions are free, but the good stuff requires payment. Still, it is legal, safe, and widely used.
A limited "shareware" version is available for older, pre-2006 vehicles. While the basic version is free, unlocking advanced features like "Basic Settings" or "Adaptation" requires a one-time registration fee of $99. New Features in Release 22.3.1 vcds 2231 free
Many users recommend blocking the program in your firewall or editing the If "free" is your main driver, OBDeleven’s basic
Here’s a factual write-up on the topic: If "free" is your main driver
