The JSON-taglib code uses Subversion as its source control system. You need to have a Subversion client installed to checkout the source code.
Check out the code with the following command:
$ svn checkout https://json-taglib.svn.sourceforge.net/svnroot/json-taglib/trunk json-taglib
cd into the directory you checked the source out into and execute the following command
$ mvn package
This will compile, test and package the taglib. The resulting jar file can now be found in the target directory.
To build this project website, cd into the directory you checked the source out into and execute the following command
$ mvn site
This will build the complete site, including all project reports. The resulting site can be viewed by pointing your browser at target/site/index.html