If you really want a challenge / something different - have a look at RMoX
. It's only experimental, but it has two very special words to describe it: "process oriented." Not yet usable as a day to day OS, but very interesting stuff.
Why can't you get opensolaris going? If you struggle on that front then I highly doubt you'll be able to get anything more experimental up and running.
hes starting to work on SkyOS again
hes trying to use the Linux Kernal
It said a few months back that he was working on a proof of concept, but this was a few months back, there haven't been any updates since and even then things weren't definitely progressing.
Personally though I do wonder what the point of it is. It's not (yet) open source or free, it's old, pretty unsupported, development basically halted years ago and community support is nigh on non existent. From what I've seen, it doesn't really have any stand out features either. Linux is open source, free, has lots of community support, more fully featured and development is progressively very actively...