I for one am excited to hear about this move and was wondering if it would ever happen. This will help keep SQL Server alive and growing (I think) and who knows, maybe bits and pieces will even become open source some day (that's optimistic perhaps).<p>I am an equal opportunity consumer of database technology - something we all should be (e.g. use the right tool for the job when appropriate). I have used MANY different databases, open source and commercial, and there are better ones and worse ones across the spectrum. I think it is naive to criticize this move in any way - it is giving more choice so should be supported.<p>That said, SQL Server has a low barrier to entry, a very good implementation of the SQL language, an advanced optimizer, strong storage engine, management tools and a lot of nice BI features. Although you don't hear about it much, SQL Server also has Parallel Data Warehouse (PDW) which is their MPP database - ironically which used to be built using Ingres and Java of all things.<p>In my experience, SQL Server <-> PostgreSQL is the closest commercial to open source comparison (core database engine-wise) I can think of. This makes sense when you consider - both of them started as Ingres! Of course, Postgres and SQL Server have totally different user experiences (database management, tooling, etc.) and many different features.