From Daniel’s comp.sys.apple2 post:

I wrote a forth style Apple II cross assembler:

http://krue.net/sixtyfive/

sixtyfive is a forth style assembler. It’s only been tested with gforth, but I’m open to adding support for others if it’s not too much trouble.

sixtyfive supports 6502, 65c02, and 65c816 opcodes.
sixtyfive can output a limited set of OMF files.
sixtyfive can compile resource definitions.
sixtyfive can make ToolBox calls (they’re not all added yet though).
sixtyfive can output ProDOS disk images.

Em is the former editor-in-chief of A2Central, as well as a blogger and rescuer of classic manuals and books.