I write about some of these systems in Chapter 5 (Influences And Other Paths) of Thinking With Tinderbox.
One thing worth mentioning is that, a couple of decades ago, it was not uncommon for consequential tools to vanish because their developer or their platform vanished. For example, when Doug Engelbart at Tymshare lost his PDP-10, there wasn’t any more Augment; if you used Augment, you were stuck.
That doesn’t really happen any more. Indeed, you can run Engelbart’s Augment again in a simulator, and you can read the files; Engelbart’s biographer did it. Things that were just too difficult to be worthwhile in 1990 are better now.
Between better file formats and better software tools, you’re likely to be able to find a life raft in case of emergency. But I don’t expect you’ll need one.