It is my understanding that the DSLs, textual information, etc. are just text and therefore are more than suited to being housed within something like TFS. I think that the purpose of the repository being within SQL Server is because the creation of the structure is only half of the story. The other half, is the runtime consumption of the information stored witin that repository and even updating, inserting information into the database. It is probably more of a mental leap to think in terms of moving from the model being a design-time artifact to a runtime one in the form of model-supported or model-driven applications.