But why now? There must have been a good reason for Sun to continue developing their own UNIX variant. I can understand the value-add coming from ZFS, but why having to maintain your own kernel? They could have built their own Linux/BSD distribution with ZFS and any other Sun-branded additions. I guess my question is not "why now" but rather "why not 5 years ago".

I don't really know much about Solaris, just trying to understand the business reasons behind their decision to compete with Linux kernel.