If they made kernel changes, and choose to respect GPL, I'd be interested to see those sources...
There are no links to sources on their site, and they don't provide datasheets. To request sources under GPL you need to get binaries first. I live in Russia, and I've never seen Elbrus in real use anywhere. It's not marketed or sold to general public. I think target market is government's security agencies. Of course they get sources anyway for audit and have no incentive to publish them.
[1] (russian) http://www.mcst.ru/os_elbrus
This is a common misconception, at least as far as GPLv2 goes. If you're distributing commercially then you have two choices:
1) Include the source when you distribute the binaries (GPLv2 3(a)) 2) Offer the source code on demand to any third party (GPLv2 3(b))
Of course, Elbrus may be distributing under the first of these, but if it's the second then there's no need to obtain binaries in order to make a request for source.
Company I work for once tried to get linux kernel sources for an embedded system produced by another russian company. We got just honest "we have our proprietary module in our linux tree, so we won't be giving you any sources. Still, we are nice enough to recompile it for you with options you need." Ugh...
The libelpthread caught my eye -- a "version of libpthread, optimized for operation in hard real time" (according to bing translator). And there's a paper in English about this: http://www.mcst.ru/doc/1107/PCS223.pdf
They also state that in realtime mode it's possible to set up different modes of external interrupt handling, "computation scheduling", "disk i/o" and "some other things", whatever that might mean. Kernel is modified to support realtime operation too.