Since we do not maintain old versions of software, we do not have a need to grid out the support for various versions of SQL, since we no longer sell old versions of the SDK and that information wouldn't be pertinent.
Basically the latest v10 supports 2005 up to 2012, and SQL 2000 "should work" ,ie it includes the codebase for 2000, but it is no longer tested. We will endeavour to fix any problems in SQL 2000 if they appear in the latest version.
SQL 7 support disappeared way back in the v4 timeframe.
Less than SQL 7 was never ever supported by Red Gate.
Hope this helps!