Just wondering if it's possible to use the SSE library as a plugin in apps like logic, cubase, etc... under the kontakt player just as you would VDL 2.5 as a plugin? or are these sounds restricted to Sibelius? Thanks... Peace!

I don't think so....SSE is a proprietary plug-in like Kontakt Gold.

I'm pretty sure that because a lot of the SSE sounds are a subset of other commercial libraries, they don't let 'em out of the barn.  To me, that makes it pretty useless, unfortunately.  I just skip right to my best libraries and run them in skinny to start.

Correct. Sibelius Sounds Essentials is proprietary to Sibelius 5 and will only appear in Kontakt Player 2 when you're running it within Sibelius. There is no way to use SSE within other host programs.