What if the core datamodel is for read-only purposes? Applications could each have their own database and connect to the core database for read-only purposes.

If all the databases reside on the same server then this should be pretty solid based on my past experience. The core datamodel could be accessed through SQL by basic dot notation by prefixing the table name with the database name.

Like I mentioned based on my experience 5 years ago in SS2005 linked databases were pretty solid - I'm not referring to linked servers in this scenario....