Solaris did not go open source. Oracle killed open source Solaris long time ago. Google,Facebook and Amazon were big from the start and needed specific hardware and software combo for their use cases. Solaris used to host 99% of the internet then Linux took off and it was cheaper and just good enough. Oracle failed to catch up and lure developers and companies in. Basically what Oracle did was that it "refused" (meaning poor service and support even if you paid a lot) to work with non-fortune 500 companies. It's still being used in most of your banks,insurance companies and large corporations all around the world. Oracle considered itself better than others and failed miserably to deliver. Also a lot of really neat futures that got into Linux were built on top of the giants from Solaris communities. It's really a shame to lose all of this.

Solaris _absolutely_ "went" open source in the form of OpenSolaris. Oracle re-closed it, but the main line of innovation in that line of operating systems (arguably all operating systems) is still open source in the form of Illumos.

The past is filled with superior technology that died due to non-technical reasons.

1) Amiga (Seriously 7 years ahead of everyone else)

2) BeOS (Unless you used it and saw it you still don't understand why it was awesome)

3) Digital Alpha Chips (I had a soft spot for old VAX what can I say)

4) SPARC was awesome but you have to remember it was awesome over Windows, Apple Server (Um anything was better then that spawn of Satan) and the various other UNIX systems.

Solaris lives on in spirit with ZFS

Do you have a link?