August 2011 update: Plans have changed, a free version of the DMM plugin is part of Autodesk Maya 2012.

See the obsolete press release at http://www.amd.com/us/press-releases/Pages/amd-ecosystem-2010mar8.aspx

Related link: http://www.thinq.co.uk/features/2010/3/8/amd-gives-away-gpu-physics-tools/