XForms for OpenSolaris 2008.11
I just uploaded a Mozilla XForms XPI for OpenSolaris 2008.11 (x86). Give it a try!
http://philipp.wagner.name/mozilla-xforms
Building Mozilla on OpenSolaris is fairly straightforward, simply follow https://developer.mozilla.org/en/Solaris_Build_Prerequisites. I needed to disable the crash reporter (but that's not needed for XForms anyways).