tar xvfz VIAJavaAPI-0.1.tar.gz
will create a VIAJavaAPI-0.1 directory with two subdirectories, reposapi and vsmf. Each of these contains three compressed .jar archives, which most Java IDEs will allow you to use directly without unpacking them. (Generally you would use an "add library to classpath" command and select reposapi.jar, and then "attach" reposapi-src.jar and reposapi-doc.jar to that library entry.) You can also compile code against reposapi.jar and vsmf.jar by including those files on the classpath when compiling.
However, if you would like to unpack the archives to inspect their contents directly, you can do so in this manner:
jar xvf reposapi.jar jar xvf reposapi-src.jar jar xvf reposapi-doc.jar
