IIUC he's been isolated- doesn't get any real funding from NIH, or from the university (beyond the standard salary), and doesn't have an active lab.
It would likely cost the university more in legal fees to get rid of him than keep him until he goes away.
He was investigated but it was dropped as being protected by his academic freedom: https://www.science.org/content/article/berkeley-drops-probe...
He also, that I know of, still supports this position. To this day, you will find people getting into this particular conspiracy and rejecting treatment. It doesn't go well for them.
I do think that freedom of speech is important, and that many attempts to squash "misinformation" are misguided, but some speech has consequences. Personally I find Duesberg utterly reprehensible and morally culpable.
Yet apparently to this day he draws over 200k/yr in salary from Berkeley. I believe they are not entirely funded by tuition/endowments which means California tax payers support him at least in part.