SqlServer was, when we created that predicate, the only database with built-in full text search. As these things are db specific, and version dependent (Oracle for example doesn't come by default with full text search in all versions IMHO), we didn't add others, as it depends on what the user uses: adding a predicate would suggest that the user can use full text search, but that's not always the case on the target db's.
So, if you want to use it on your db, I'd take the FullTextSearchPredicate class from the runtime sourcecode, and create your own copy in your own project (leave the ID the same). So i.o.w.: only change the SQL fragment that's to be emitted.
For Linq for example we didn't add a specific full text search fragment, but it's easy to add through a function mapping (as described in the documentation). This to avoid having db specific predicates.
