It can't be mounted natively.
I guess one major issue is that ReiserFS use the GPL license which forbid reusing any reiserfs code on Solaris (even OpenSolaris if I'm not mistaken), so it should be rewritten from scratch ...
Should ReiserFS be released under LGPL instead, I think that would ease the port.
However, by running a linux layer, e.g. QEMU or LAE (Janus), it seems be doable.
See a similar explanation with ntfs at:
http://blogs.sun.com/roller/page/the...8se_under_qemu
