Nothing really, but you can’t just assume that any package built for any version of fedora will somehow work on Rocky.
If ‘mapserver’ means ‘https://mapserver.org/’ and ‘GitHub - MapServer/MapServer: Source code of the MapServer project. Please submit pull requests to the 'main' branch.’, it’s annoying that they jumble up all the code and the build system, and don’t explain the build in the readme. You have to guess which file to look at, and I’m guessing it’s ‘INSTALL.CMAKE’ in capitals, which gives a good overview of how it’s supposed to work. The only sensible thing I can see, is where it tells you to do an ‘out-of-source’ build.
There’s also a forum post about building from source, e.g. setting up build dirs, and installing ‘devel’ packages, step, 1, 2, 3
‘Gaming in Rocky - #25 by gerry666uk’
In the meantime, maybe they’ll add it to ‘epel’ or something.