Symbolics offered Macsyma on other platforms.

Eventually, I assume. But when they got the licence they tracked down every copy of VAXSYMA and demanded the org stop using it and return/destroy all of the IP. And while I'm not familiar with the long term history of Macsyma at Symbolics, there's lots of talk about the reluctance of those outside its unit to sell or push it on non-Symbolics Lisp Machine platforms. As far as I know, it wasn't available for LMI's LAMBDA or TI's Explorer, although perhaps that changed as Symbolics' fortunes declined.

My reading on Danny's take on Symbolics comes from when I was working for LMI in the September 1982 to June 1983 period. Due to the ADL/Symbolics single source licencing scam (which also, I'll note, cut out Joel Moses, the "father" of it and others, something he was still unhappy about at the end of the '80s), he didn't want to buy from Symbolics, and asked me if there was any chance LMI could deliver in the time frame he needed for the founding of Thinking Machines, which was incorporated in 1993.

I regretfully had to tell him there was no way that would happen (success was not even in the picture until I recruited a extremely talented classmate right after he graduated in 1983), so they bought ~6 3600s to get the company off the ground (in part limited by the power available in their interim Watham office), and as you note, it was one of the front ends you could buy for the original formula Connection Machines (in black trade dress to fit with their stunning industrial design). Understandably, he wasn't willing to give up on his Comnection Machine dream because of Symbolics's behavior at that time.

Stallman was reading other people's mails and he was threatening to sabotage other people, wasn't he?

"Everybody" read other's emails, Joel Moses' was particularly fascinating. Of course there was an ethos about what you'd do with that information, and one I can see RMS violating.

But the only sabotage rumor I heard was WRT to a conflict he was said to have with Dan Weinreb. As the story went, on the basis of a technical dispute WRT to the Lisp Machine's software, RMS threatened to not only delete all live copies of this bit of Dan's code, but also their copies on backup tapes. Dan's response was to accept a job in Livermore, CA to work on the ambitious S-1 project (this looks good, just skimmed a bit of it: https://forum.stanford.edu/wiki/index.php/S1_project), which had very strong connections with this MIT community (the Chaosnet actually extended all the way over to it, I forget which is which, the other end was the most geographically east node in the MIT EECS machine room, one Trantor, the other Terminus), and for example GCC started with a failed port of its Pastel compiler.

When Dan returned, he flatly denied the rumor, and I found him credible, especially since threatening to mess with ITS backup tapes like that was a cardinal sin.

Lessor methods of sabotage, certainly obstruction, would certainly fit with RMS's style, but I can't remember hearing of any significant examples. And I'll note his response to all this craziness was to do GNU/the FSF, which was ideologically aggressive, but otherwise constructive. We are, after all, people who make things, not destroy them.

Note on my (claimed) credibility: I was on first name business with all of the people I've named in this post, was even a roommate of RMS when he launched the GNU Project.