TMSU is described as 'Tool for tagging your files. It provides a simple command-line tool for applying tags and a virtual filesystem so that you can get a tag-based view of your files from within any other program' and is an app in the os & utilities category. There are more than 10 alternatives to TMSU for a variety of platforms, including Windows, Mac, Linux, Self-Hosted and Microsoft Edge apps. The best TMSU alternative is TagStudio, which is both free and Open Source. Other great apps like TMSU are TagSpaces, Tabbles, Keepmark and allTags.
File tagging is secondary functionality, tags only available inside software.