Dear Peter,
I think the GNU APL layout differs a little from the Dyalog layout. It would be nice for your Mac setup to match the output of the GNU APL ]ketb command. That is what I did with my layout files.
I used the Mac primarily for several years. I had a problem with my motherboard. While they were fixing it, I switched to LinuxMint as my primary platform and haven't gone back. (I had many years of Unix & Linux experience. I just didn't use it as my primary development platform until the last year or so.) I like the idea of having the software portable so that I can switch and share at will. Your Mac layout is appealing for that reason. I'd like to get one of my Mac's up with GNU APL, but I haven't done it yet.
Thanks for your work on the Mac files!!
Blake