Logging App SD by EI5DI is free and unrestricted…. 

SD logging App now free

With effect from January 1, version 21 of the logging App SD by EI5DI is free and unrestricted

SD supports RSGB, UKEICC and IRTS HF contests, and hundreds of others worldwide.

SD runs on Windows, and on Linux with Wine, and on Raspberry Pi 3 with
Wine and Exagear (from eltechs.com)

No registration or key file is required.  SD will continue to be supported and
updated, and users can request help by emailing
sd-user (at) contesting.com

Further information on SD is at