On my dev machine, I have SQL Management Studio 2008 R2 installed. I tried to upgrade to SSMS 2012 Express, setup finished but nothing happened.
Is it possible to get SQL Management Studio 2012 without occurring a license on the Database Engine itself?
Yes, it's possible.
Installing SSMS 2012 isn't really an upgrade, it's a separate installation of a newer version, so you basically have SSMS 2008 R2 and SSMS 2012 installed side by side.
Besides SSMS 2012 Express, you can also install SQL Server Data Tools which is a free "integrated environment for database developers to carry out all their database design work for any SQL Server platform".
