GNU APL comes with a file named apl.xkb under the support-files directory. I just did some testing of it with a normal (non-apl) keyboard. The mappings in that file are way out-of-date and do not match ]keyb output. That would also be true of the compiled version of that file - apl.xkm.
I then tested my WASD map file - apl.wasd.xkb. That file correctly maps a non-apl keyboard to map correctly with ]keyb output.
Although my WASD config file was made for my WASD keyboard design, it also completely correctly maps to non-APL keyboards too.
I suggest that:
1. support-files/apl.wasd.kbd be copied to apl.xkb
2. remove apl.xkm
3. Update the docs to use apl.xkb rather than apl.xkm (just substitute apl.xkm with apl.xkb in README-3-keyboard
Thanks.
Blake