Maybe rename Operating Systems to "Storage Platforms" or "Storage Software" or similar.
Then maybe re-org the forums based on how 2011 is likely to shake out in terms of popularity and installed base:
Windows Server, Windows Home Server, Small Business Server
FlexRAID, unRAID
FreeBSD, ZFSGuru, and FreeNAS
Solaris, Nexenta, OpenIndiana, and napp-it
And if you can't live without it, Apple OS X Server, though I predict it being a completely dead forum as far as activity.