The University of Tennessee Digital Library Center has released version 1.2 of the DLC-MODS Workbook under a GNU General Public License. A demo is also available.
Here's an excerpt from the diglib announcement:
The DLC-MODS Workbook provides a series of web pages that enable users to easily generate complex, valid MODS metadata records that meet the 1-4 levels of specification outlined in the Digital Library Federation Implementation Guidelines for Shareable MODS Records, (DLF Aquifer Guidelines November 2006).
Developed by programmer Christine Haygood Deane under the direction of metadata librarian Melanie Feltner-Reichert, this open source client-side software provides control of date formats and other problematic fields at the point of creation, while shielding creators from the need to work in XML. Metadata records created can be partially created, saved to the desktop, reloaded and completed at a later date. Final versions can be downloaded or cut-and-pasted into text editors for use elsewhere.