Apache Commons Daemon is a good alternative. It has Procrun for windows services, and Jsvc for unix daemons. It uses less restrictive Apache license, and Apache Tomcat uses it as a part of itself to run on Windows and Linux! To get it work is a bit tricky, but there is an exhaustive article with working example.
Besides that, you may look at the bin\service.bat in Apache Tomcat to get an idea how to setup the service. In Tomcat they rename the Procrun binaries (prunsrv.exe -> tomcat6.exe, prunmgr.exe -> tomcat6w.exe).
Something I struggled with using Procrun, your start and stop methods must accept the parameters (String argv). For example "start(String argv)" and "stop(String argv)" would work, but "start()" and "stop()" would cause errors. If you can't modify those calls, consider making a bootstrapper class that can massage those calls to fit your needs