I generally agree with what little I understand of the principles behind his work. But "selling out" for money (and locking up code to facilitate that) was the trend he was defying and it's a vastly easier path than the one he chose.
In 1990 Stallman received a MacArthur grant, which comes with $500,000. During the late 1990s, many of the founding fathers of free software were granted stock during IPOs. Here for example is documentation that Eric Raymond got stock that ended up being worth $36 million (for a couple of years until the bust in 2001): https://www.theregister.co.uk/1999/12/10/ipo_makes_va_linux_...
Now Eric Raymond got that stock for accepting a position on the Dot Com's board of directors, and I can well imagine Stallman refusing all such directorships on principle, but OTOH I would be surprised if none of the founders of successful Dot Coms during that period donated generously to Stallman directly or via the FSF.
In general, almost everybody with as much fame and public reputation for moral rectitude ("prestige"?) as Stallman has for as long as Stallman has had it is worth at least a million or 2 dollars (unless they're, you know, chronically mentally ill or some such). Fame and prestige for example get you much higher speaking fees, and public speaking has long been Stallman's favorite thing to do.
So it took him seven years to get that money. Meanwhile, he was intermittently homeless and only succeeded in registering to vote while homeless due to his fame for his work. He submitted his voter application and listed himself as a "squatter" at his work address. The registrar of voters refused to accept this and changed their mind when an article about him came out in a national publication and said the same thing.
Meanwhile, I routinely hear that software engineers at FANG companies can make upwards of a quarter million annually in salary and he lives in Boston, not known for its low cost of living.
That should be common knowledge for the HN crowd, so I'm not going to try to back that up with a source.
I always thought the "squatter" description referred to his spending much of his time at MIT and keeping things at MIT without being employed by MIT. (Stallman quit his MIT job when he started GNU out of a worry that if he kept it then MIT might claim ownership of GNU; the legal ramification of the GPL weren't understood as well back then as they are today.) I don't think his use of the word implies that he had nowhere else to live.
I searched the page you linked for "home", "squatter", "vote" and "register" without finding any text the supports anything in your comment. I hope I don't come across as antagonistic to you; I am sincerely curious whether Stallman was ever homeless (i.e., ever lacked reliable access to private indoor space with a door that could be locked).
A quick search of the web also gives me nothing and I don't plan to spend a lot of time trying to prove this. Perhaps this will suffice as a source to satisfy your curiosity:
ADDED. "Until around 1998, my office at MIT was also my residence. I was even registered to vote from there. Nowadays I have a separate residence in Cambridge not far from MIT." https://stallman.org/rms-lifestyle.html
Not trying to argue with you. I just honestly don't understand it to work exactly like that, but some of your phrasing seems ambiguous and I'm wondering if I even understood you.
IBM bought Redhat at a valuation of $34 billion.