The kernel ABI is stable between major version numbers. It is never intentionally broken between majors. More importantly, the kernel APIs are very stable, which seems to be intentionally broken on Linux regularly.

Userland ABI is much more stringent, pretty much any commercially used OS will maintain compatibility for old applications indefinitely, Linux and Free and Net BSD included.

> which seems to be intentionally broken on Linux regularly

Please provide evidence to back the claim of intent. This comes across as if you're implying malice, when it's far more likely interfaces change in the natural course of development where there are no restraints like abi/api stability commitments.

Torvalds himself said he’s breaking it intentionally to prevent people relying on it.

Was this in a mailing list thread? Got a URL? I'm unaware of this.

Yes, especially for the y part of X.y. [1] Although since version 7 multiple symbols are supported. [2] If you're interested in what the release engineering team has to say about it this page [3] contains more details.

[1] https://wiki.freebsd.org/Releng/ABI [2] https://wiki.freebsd.org/BinaryCompatibility [3] https://www.freebsd.org/doc/en_US.ISO8859-1/articles/freebsd...

Yes, the *BSDs, all proprietary UNIX variants, Windows, mainframes and pretty most everyone else with exception of Linux.

FreeBSD has a stable kernel ABI for each release and is allowed to break it in a new version. This allows nVidia to have an easier time providing binary drivers on FreeBSD.