On MacOS-X you can build this framework for use with native MacOS-X applications using xcode with no special additions. The Examples subdirectory is however, GNUstep specific and requires the installation of various GNUstep components if you wish to run it on MacOS-X For rudimentary testing on MacOS-X, you can build and run the testWebServices target in xcode, but you must have installed the WebServices framework first.
gnustep/libs-webservices
The WebServer library contains a collection of classes to be used for creating client and server 'web service' applications
Objective-CLGPL-3.0