The Glitch Works looks like a good place to explore - if you find anything which especially piques your interest please leave a note!
Found via a project in their github repos as announced on the 6502 forums:
Today, we’re releasing our work on dumping some original Rockwell RSC-FORTH ROMs:
GitHub - glitchwrks/rsc_forth: Rockwell RSC-FORTH for the R6500 familyI understand a number of folks here have been interested in getting these ROM images online for a while ! We’ve also done patches to make RSC-FORTH compatible with our Glitch Works R6501Q/R6511Q single-board computer. TangentDelta put together a ROMFS image and updater for that:
GitHub - glitchwrks/r6501q_romfs