Is it possible to use the Oracle tools with one of the "free" Visual Studio distributions? If so, could it be used as an alternative development environment for SQL Developer?
Sorry - that should have read "alternative development environment to SQL Developer.
Can we edit packages, procedures, etc. Can we execute queries and explain plans?
Oracle Developer Tools will not work with Visual Studio Express Edition since that edition does not allow "Add-ins".
So the answer is yes, you need a Visual Studio license to do what you are requesting. You can still use the Express Edition if you are only hand coding .NET code that uses ODP.NET.