Apple - Are tags portable, and if so how?

Tags are not 100% portable in that they don't always survive mailing or copying to other computers such as Linux or Windows. On that respect, it's more about those OS supporting the Apple filesystem. I am impressed that even copying tagged files to a SMB formatted USB drive preserves the tag metadata and most copy operations from and to another Mac via an HFS+ hard drive or share does preserve the tags well in practice. (Even copying the file to a 10.8 or older Mac didn't strip tags in my tests).

Apple's article covering tags, http://support.apple.com/kb/HT5839, recommends:

If you want to include your Tags when sending files through Mail, Messages, or other apps, compress your files and folders before sending them.

Yes, tags are completely portable as they are saved to the file as extended attributes. Copying/moving the file keeps the tags as they are saved as com.apple.metadata:_kMDItemUserTags to the file.