I wonder why. Uses third-party code? Some contractor/consultant/etc wrote it and they can't find the contract so they don't know what it says about copyrights? Lost it completely?

Likely something like that. My money is on them being unable to locate someone who needs to give permission, and it's probably not a very high priority issue.

I vaguely recall reading a blog post when Sun opened the Solaris source code, that it was a tremendous effort tracking down every single person they needed permission from.

And then Oracle went and undid almost all that work :'(

To make it even worse, they laid off most of their Solaris developers a couple years ago.

Somebody who used to work on Solaris before the Oracle takeover commented at the time that just by looking at the number of layoffs, Oracle Solaris was effectively dead.

I am not even a big Solaris fan (although it was the most beautifully named OS ever), but I cannot help but think of Rutger Hauer's dying speech from Blade Runner: I have seen things you people would not believe [...] All these moments will be lost in time like tears in the rain.

If somebody who has been there would write a book about the development of SunOS and Solaris, I would probably buy two copies. If the title included the word Eclipse, I'd buy three copies.