It will run on SQL Server, it's just not an "out of the box option".
You have two possibilities for this... with 2.1.7, there is a sqlserver directory under the WEB-INF/config/database
directory. You can use this with the manual install process to get it working with SQL Server.
Or, if you don't mind using the older version 2.1.6, you can use my TorqueDAO implimentation. See:
https://coderanch.com/t/576609 #13551
[originally posted on jforum.net by monroe]