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.
It’s incurable but usually has a good long term prognosis (97% 5 year survival rate and most people live 20+ years from diagnosis). Seems that the best RMS will get is remission but not cancer free.