Typically the approach taken by people who are concerned about legal issues regarding disassemblies is that they distribute a script file that contains all the code/data annotations, comments, variable names, and labels, and then the user can feed this file and a copy of the original binary into the disassembler to reproduce the disassembly. Here's a random example for a 6502 codebase: https://github.com/TakuikaNinja/FDS-disksys . IDA Pro has this functionality built in, you can export a .idc script file that will reproduce the .idb file if you load the original binary into a fresh instance of IDA Pro and then run the script. Maybe Ghidra has something similar, if not I bet you can get your AI to write export/import scripts for Ghidra.

> It's highly likely that the original implementation language was assembly.

Agreed. I did a bit of development on a TI-84+ years ago and I was not a skilled programmer back then so only used TI-BASIC, but the fact you could only write apps in assembly makes me think the operating system was the same. ticalc.org had a gcc fork from memory though I don't recall which calculators it targetted.