What's the problem we're trying to solve?
gnu common uses include:
- specific reference to Hurd or other OS-related components of the GNU operating system
- decoration on general Linux questions not specific to GNU components
- context to differentiate characteristics associated with the GNU version of various *nix utilities
- collective tag for various GNU Project applications or utilities that don't have a dedicated tag
- decoration referring to the GNU Project when that doesn't add value, such as using it in addition to a product-specific tag
- a generic term for open source
Many of the common uses are no-brainers for cleanup (bullets 2 and 5). Bullet 6 is incorrect usage and if an actual tag is warranted, it can be replaced. That leave three different "legitimate" ways it's used.
For a tag to be useful, it needs to add value and it needs to be used correctly and consistently. Anthony Geoghegan wants a gnu context tag that differentiates GNU characteristics. If 90% of the questions tagged gnu actually refer to some other meaning, the false alarms will quickly make the tag useless as a context tag.
So a tag needs to have a single, unambiguous meaning. Just a well-defined wiki excerpt isn't adequate because many users don't bother to read it. The tag name also needs to be unambiguous. This suggests eliminating the gnu tag and replacing it with a tag for each purpose.
My suggestions, with the rough wiki excerpt:
gnu-hurd Use for questions specifically about the GNU kernel (Hurd), or GNU operating system components (including their usage in a Linux distro). See the full wiki for guidance on appropriate tags for other uses.
gnu-differentiation (need a better tag name but I haven't thought of one, yet; ideas?) Use as a supplemental tag to differentiate questions relating to GNU Project software that differs from the POSIX standard or their BSD equivalents. See the full wiki for guidance on appropriate tags for other uses.
gnu-project-apps For purposes that don't involve differentiating characteristics that make GNU programs different, this is classic manufacturer meta tag usage. Knowing that a program was developed by the GNU Project doesn't provide useful information for any specific program (and the list is extensive). So the guidance should be something like:
Do not use this tag. For questions pertaining to a specific program from the GNU Project, use a dedicated product tag if it exists, or use a generic tag that refers to the program's function. See the full wiki for more detailed guidance, including appropriate tags for other uses.