If you look at
/opt/webwork/libraries/webwork-open-problem-library/OpenProblemLibrary/macros
you will see the directories
CollegeOfIdaho/
Dartmouth/
FortLewis/
Michigan/
NAU/
TCNJ/
Union/
WHFreeman/
These contain macro files used in problems contributed by the named institutions. Of course a problem using the macros has to load the necessary files(s). In order for WeBWorK to find the files, in defaults.config you will see the code:
$pg{directories}{macros},
"$courseDirs{templates}/Library/macros/Union",
"$courseDirs{templates}/Library/macros/Michigan",
"$courseDirs{templates}/Library/macros/CollegeOfIdaho",
"$courseDirs{templates}/Library/macros/FortLewis",
"$courseDirs{templates}/Library/macros/TCNJ",
"$courseDirs{templates}/Library/macros/NAU",
"$courseDirs{templates}/Library/macros/Dartmouth",
"$courseDirs{templates}/Library/macros/WHFreeman",
If you contribute your problems to the OPL, we could add your macros to the above. If you want to set up you own server in a similar manner, I would suggest editing localOverrides.conf adding the above code from defaults.config plus whatever you call your new macros directory.
Arnie