The first error when URestrict loads looks as though you aren't using ULib SVN, or at the least, an older version is also somehow conflicting. "cmds" is part of the new SVN, if it's nil, the SVN version of ULib isn't loading (right).
As for the second error, no idea. Googled the FCVAR thing and found tons of stuff about Source servers in general, not just Gmod.
It's a Source engine issue in some way, not just Lua.