Development Tools
Integrated GNU Compilation System
GNU Source Level Debugger
GNU Make, bison, flex, rcs, cvs, indent patch, autoconf, dejagnu …
Graphics Libraries (aalib, Mesa, Xaw3d, Gd, Gtk+, Imlib, Jpeg, Mpeg, Png, Tiff, Xpm, Zlib, …)
SCO Packaging Front-ends (mkpkg)