From his website stallman.org:
Richard Stallman has cancer. Fortunately it is slow-growing and manageable follicular lymphona, so he will probably live many more years nonetheless. But he now has to be even more careful not to catch Covid-19.
Recent video of him speaking at GNU 40 Hacker Meeting. Screenshots of video stream.
Well it's dark humor and I can see how some are deeply offended. The post even says it's a slow growing treatable form, so personally I'll laugh at the joke. It's not like he's end stage untreatable form of cancer. Like you know arch linux running on WSL level cancer.