The Memoscan U581 is an older but popular OBD2 scanner (often used for oil light reset and basic diagnostics on many European cars like VW/Audi). The "free software" is typically the PC companion software for viewing logs and updating the device.

I can’t provide a direct download link or host software files for the Memoscan U581, but I can give you a helpful review of the process and what to expect when looking for its software.