having now poked at the source code on github, yeah this is not at all maintainable by modern standards. it's the kind of code you're unable to modify until you memorize every last line and the whole problem domain.
I'm not at all worried that particle physics will slow down (...heh) because of this. It sounds like the one guy has been doing an incredible job of service maintenance over the years, sure, but these folks write software all the time.
I have a hunch that FORM is not made up of easy to grok software designs or it would probably be true that other folks would have contributed in a bigger way regardless of academic stimuli. If that is indeed the case, as is common in research-academia software product, then tie a bow on it and send it off to the Smithsonian.
I would be really quite surprised if some enterprising 19 year old whiz-bang genius from Iceland didn't re-write it in Mathematica.
I've built tons. Most of them don't stick for long. One that has is a file-cabinet organization tool - https://github.com/robacarp/place
- it moves files into place within my filing system
- renames the file so that even if it's moved _from_ the filing system I can see where it came from (eg sent in an email)
- uses a custom TUI engine I built for this specific task https://github.com/robacarp/keimeno
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Another is a clean, bare bones, web-extension mode "picture on a new tab" extension. When I came back to firefox a few years ago I couldn't find one amongst the clutter on AMO so I put together https://github.com/robacarp/photographic_start
> a popular gradually typed language that natively allows writing both dynamic and type-safe code, allowing quick prototyping and then gradual refactor to type safety.
You mention it in your edit, but Crystal has been exactly that for me. A rubyist for a decade I found Crystal to have the type system I was expecting all along.