Recently, all entries with Russian email addresses were removed from the Linux MAINTAINERS file which lists people "maintaining" parts of the kernel. "Maintaining" here means, if I understand correctly, that they keep their part of the kernel in working order by reviewing and merging code from others. They often also contribute code themselves, but that is not a requirement.
The reason stated for the change was "various compliance requirements". Now I would understand fears of backdoor injection, and I understand that Linus feels hostile towards Russia, but I have a hard time seeing how sanctions apply here: The contributions are essentially gifts (even if the contributors may be paid to produce them by Russian companies). it is also noteworthy that the MAINTAINERS file is informational only: It provides links to people that can be contacted with questions or patches. The file also does not carry a copyright and therefore, unless I miss something, simply falls under the GPL.
The patch was supplied by Greg Kroah-Hartman who is, like Linus Torvalds, employed by the Linux Foundation which is based in San Francisco, thus underlying U.S. law. But the Foundation does not "host" the Linux kernel.
How do American sanctions affect Linux? What role does the Linux Foundation play? After all, Linux is hosted on a distributed version control system (even if the actual development is essentially broadly hierarchical, with Linus as the final arbiter).