(In this mail, "gnu-apl-mode" refers to the Emacs mode that I have built, which "GNU APL" refers to the GNU product of the same name).
The Emacs mode has support for searching and automatically displaying documentation (it also integrates with Eldoc). There is code in there to detect whether the function is used in a monadic or dyadic context and instructs Eldoc to pop up the correct documentation.
I fully agree with you that the documentation really doesn't belong in the gnu-apl-mode itself. It really belongs in GNU APL. That said, no matter where the documentation can be found, it needs to be in some machine-readable form so that gnu-apl-mode is able to access it.
As for IBM's documentation, I approached them and asked if they were willing to license the reference documentation in a form appropriate for this project. They did give me a license to use it, but that license is tied to gnu-apl-mode. This is the reason I would like to replace it with something that is GPL compatible.
Since I had the license to use it, I did put it in there, but as soon as this thing goes into ELPA, it will have to be removed. Since I'm now close to actually doing this, I felt it was time to try once again to get help with the documentation.
Finally, I have worked very closely with Jürgen who is the maintainer of GNU APL. I don't think he's opposed to including documentation in the GNU APL package (as opposed to gnu-apl-mode) but including the IBM documentation is obviously out of the question.
In summary: Yes, the documentation belongs in GNU APL proper. And if free documentation can be produced, it will most likely be included in GNU APL itself, with gnu-apl-mode simply accessing it.
Regards,
Elias