I think NetX can run on Windows.
IcedTea-web uses an improved version of the NetX codebase for its javaws implementation.
the javaws launcher is currently mostly a shellscript around the icedtea-web/netx.jar so this can probably be used without recompilation on Windows.
To date IcedTea-web have been ported to run on:
Linux packaged for all major distributions and arch.
FreeBSD
http://svnweb.freebsd.org/ports/head/java/icedtea-web/and... OS2 (eComStation2) ->>
http://svn.netlabs.org/java/wiki/IcedTea-WebIt should be easy to port the plugin and javaws anywhere.