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RDBMS systems are not particularly good at full-text searching to begin with (I'm not quite sure how SQL Server handles this,

AFAIK SQL Server uses MS Index Server for this.

So you could potentially wrap calls to SQL Server via MS Index Server using Zope in the same way Site Server does it, if you were so inclined. I'm not. :-)

I remember I once saw a mention of ZCatalog being able to index the records of a dbms, when they were traversable through the web because it made no difference between object and record properties (both being accessible through a URL). Was this false information, or was I just dreaming?

I don't know, to be honest. I *think* this would be true of a SQL method that required no parameters. Unfortunately most SQL queries require parameters that provide the query context (even the ones reachable via "direct traversal" where the input parameter is provided by the next part in the traversal path). This is not particularly useful, even if true.