Some more info (I'm surprised at the response here!):
https://en.wikipedia.org/wiki/Advanced_Boolean_Expression_La...
"The ABEL concept and original compiler were created by Russell de Pina of Data I/O's Applied Research Group in 1981." This is false. I don't know what de Pina did, but ABEL was developed from scratch by the 7 member team listed in Wikipedia, and the grammar and semantics were designed by myself.
Is there some "copyright" printed on it? Before 1989 it was apparently "required" and if not printed apparently it matters if "the author made diligent attempts to correct the situation":
https://fairuse.stanford.edu/overview/faqs/copyright-protect...
"you should assume that every work is protected by copyright unless you can establish that it is not. As mentioned above, you can’t rely on the presence or absence of a copyright notice (©) to make this determination, because a notice is not required for works published after March 1, 1989. And even for works published before 1989, the absence of a copyright notice may not affect the validity of the copyright — for example, if the author made diligent attempts to correct the situation.
The exception is for materials put to work under the “fair use rule.” This rule recognizes that society can often benefit from the unauthorized use of copyrighted materials when the purpose of the use serves the ends of scholarship, education or an informed public. For example, scholars must be free to quote from their research resources in order to comment on the material. To strike a balance between the needs of a public to be well-informed and the rights of copyright owners to profit from their creativity, Congress passed a law authorizing the use of copyrighted materials in certain circumstances deemed to be “fair” — even if the copyright owner doesn’t give permission."
It's not simple, but maybe an interesting starting point... Maybe, if there's if it is not a product actually being sold or even used as such anymore, there's reasonable chance that the copyright holder wouldn't be interested to enforce the protection of the "historical material"?
http://www.swtpc.com/mholley/PLD_History/ABEL_project/Russ_d...
But my degree is ME, not CS nor EE.
Needless to say, the ABEL projects were frustrating...indeed a shame that it's not open source.