I created a tag
[windows-alternative] to describe a question where the OP is looking for an OS X alternative to an application that is Windows-only. It doesn't feel quite right though, maybe someone has a suggestion for better tag to describe these types of posts?
FWIW, I also think that for these types of questions, this tag should be used instead of
[osx], since it's implicit that the poster is looking for an osx application