The "Standard" / "Professional" / "Commercial" license (all the same thing) are the only variety that can be installed on up to 4 computers. The Student licenses, and Home licenses, can only be installed on one computer.
When you activate under MS Windows, by default it uses the hard disk serial number to lock against. I have recently noted in the documentation that it is possible to activate on MS Windows against an ethernet address, but I do not know how to do that.
Linux and OS-X both lock against ethernet addresses.
None of the license types are deliberately restricted to a single operating system. However, you might need some assistance from technical support to get your license properly activated in a dual-boot situation involving different operating systems.