Version 4.1.0 is a maintenance release for IT Mill Toolkit 4 branch.
Most significant change included in the IT Mill Toolkit 4.1 is the Apache 2.0 license. This allows IT Mill Toolkit 4 to be freely used in systems that previously required a commercial license.
Get it here:
http://www.itmill.com/downloads/itmill_toolkit_download-4.1.0.htm