The following was posted on the DropDMG blog:

Version 3.1.2 of DropDMG is now available. This is a free update for owners of DropDMG 3.0 that includes the following enhancements:
  • Added support for Growl notifications via GNTP (requires Mac OS X 10.7 or later).
  • When renaming a configuration, layout, or license in the preferences, you can now press the Esc key to cancel.
  • Fixed a bug where DropDMG would log an error to the console when converting a ZIP archive to a disk image.
For information about previous releases of DropDMG, please see the version history.