Interesting read (now I've read it all). I like your graph but it's a little incosistent. You include early betas in NG OS but not Workbench. Work on the MorphOS kernel started in 1998 (?) and AROS started in 1995 (discussions started in 1993). Workbench started in 1982. So maybe a striped area for beta versions (including AROS that is still beta)? First "non beta" of MorphOS came in December 2002 and AmigaOS 4.0 in december 2006.