Maybe try platform.platform()
:
>>> import platform
>>> platform.platform()
'Java-1.7.0_07-Java_HotSpot-TM-_64-Bit_Server_VM,_23.3-b01,_Oracle_Corporation-on-Mac_OS_X-10.7.5-x86_64'
There you'll find more useful methods: http://www.jython.org/docs/library/platform.html