Betasoft was the software company run by Andy Wright, who was the author of SamDOS and the Sam's ROM. Betasoft started out on the Spectrum, and amongst other things sold BetaDOS (a +D DOS), and BetaBASIC (a speccy BASIC extension)
There were many features that Andy Wright would have liked to have included the SamDOS/BASIC, but couldn't due to lack of space, so Betasoft later released MasterDOS and MasterBASIC. MasterDOS was a complete SamDOS replacement, and had features even the most basic of users would find useful. MasterBASIC was a set of extensions to BASIC, the usefulness of which probably varied from user to user. I found MasterDOS invaluable, although probably only ever used a handful of the MasterBASIC features.
Betasoft also sold some other utilities for the Sam, including File Manager (a database program), and GamesMASTER (a games design language).
I believe Andy Wright did attend some Sam related shows, although last I heard (way back in June 1993), he was working for a small company on a non-Z80 machine.