Bushnell authored GNU Hurd:

"RMS: I am not very optimistic about the GNU HURD. It makes some progress, but to be really superior it would require solving a lot of deep problems. However, mainly what I think about the HURD is that finishing it is not crucial."

https://redditblog.com/2010/07/29/rms-ama/

I think Bushnell makes some good points but:

(1) he’s biased.

(2) a Googler calling out Stallman is just rich (given the debt Google, its employees, and all modern tech companies owe free software and the relatively little they repay).