Arkham Development released some projects in open source:
Native plugins for Antiryad Gx.
Arkham Demo Group Dos and Amiga demos written in Basic, x86 and 68k assembler (from 1991 to 1998).
Arkham Demo Group 3d engines written in x86 assembler.
Arkham Demo Group DOS tools (paint program, sound tracker for Adlib, modeler, picture and 3d converters) written in Basic and x86 assembler.