And the software is most likely owned by the competitor that sells said "new" software that most likely doesn't fit the niche anymore. They normally refuse to re-license even without having to give updates/support.
I'd be pretty surprised if a judge was like "ah yes the defendant's consultancy modified a piece of industrial control software that you haven't given a thought to in three decades to make it run on a modern computer and not require a parallel port dongle, and that's definitely a DMCA violation and you've been harmed by it and deserve all the money."
"Laches" https://en.wikipedia.org/wiki/Laches_(equity) is probably a relevant concept here. In a scenario like the one you're describing, the delay is likely to be taken into account, but it's unlikely to be the whole of the argument.
That's irrelevant in many cases where you want to support existing hardware. Clean room reverse engineering for interop purposes is allowed under copyright law.
Sure, but in fairness, this thread is about bypassing the copy protection in the existing software. Which I'm also arguing is safe, but it is not as obviously safe as a clean room reverse engineering effort.
I'll reiterate my comment from a few parents up: This is currently happening, and no, the copyright holders either don't even know, don't care, or are truly gone (even as far as being deceased.)
