This is primarily a maintenance release that fixes some key issues with the original Deadline 4.0 release. The release notes can be found here:
http://software.primefocusworld.com/software/support/deadline/releasenotes_4.0sp1.php
NOTE: If you are already running Deadline 4.0, this version does not require a new license. If you are upgrading from an older version, please contact a member of our sales team at deadline-sales@primefocusworld.com.