Hi ,I have not fixed an error in remainsworthy, but I did base the new engine RebornMainsworthy on its code and fixed the error. the souce code has never before been released.
its available at Leo site in the Mainsworthy engine page
http://wbec-ridderkerk.nl/
the source code, has some easy to follow steps, it defines all move of each piece from all squares without a real-time move generator. it still has a generator but its basicaly just dropping moves from the list that are unavailable.
It dosnt check move legality.
it has very easy enpassant code to follow, eg if you move a pawn diagonaly but the square is empty then your useing enpassant, so delete piece.
it dosnt have a book, and it uses a basic algo.
Mark Ainsworth