Yes they are, any licenses are revokable. The GPL as well.
I could release software under GPL, not accept any patches, see the software grow and 2-3 years from now when a lot of people are using and depending on the software, bam I revoke the GPL from all previous versions and impose a special EULA in its stead. I can because I am copyright holder.
When my employer failed in 2002, I had no trouble getting another job offer. Unfortunately that company failed before my start date. As did the one after that.
I moved to NYC to get a semi-functional job market.
These days the possibility of highly correlated failure is a major component in my career decisions.
I firmly believe that you shouldn't author a book in something if you lack the appropriate expertise. If you do so, you risk disseminating misinformation at scale, causing enormous harm.
Ditto. DevOps is charged out at the same comparative rate Sys Admin was 10 years a ago. Which makes sense - it's boring work and not as many people want to do it.
This is not true. None of the standard BSD licenses are revokable.