Just to throw in another point here - while the development tools may be free, licencing SQL Server(s) for production use can be very expensive & convoluted.
licencing SQL Server(s) for production use can be very expensive & convoluted.
It's not convoluted at all.
Want a free on-premises database? Simple. Use SQL Server Express. That will handle a database up to 10 GB.
Want to have Microsoft host your SQL Database for you? Simple. Use Windows Azure SQL Database. $10 per month for 1GB and then $3.96 per GB per month after that up to 10 GB and then cheaper from there.
Have you ever even looked into using Microsoft software or did you just immediately dismiss it without looking at it?