Question regarding licensing: [1] states that a source file can be "one of the compatible GPL variants and alternatively under a permissive license like BSD, MIT etc."

Looking at a rust source file inside the dev tree 'Rust-for-Linux' [2], it is licensed as "Apache-2.0 OR MIT". However, Apache-2.0 appears to be incompatible with GPL-2.0 [3]. How come that the licensing in such a way is possible with the Linux licensing rules?

[1] https://github.com/torvalds/linux/blob/master/Documentation/... [2] https://github.com/Rust-for-Linux/linux/blob/rust/rust/alloc... [3] https://opensource.stackexchange.com/questions/1357/can-i-li...

Edit: Another quote from [1]: "[...], though individual source files can have a different license which is required to be compatible with the GPL-2.0:"