I've used the DMCA against GPL infringers (including the MPAA) - it generally does work in terms of stopping further distribution, but it rarely results in you getting the source code. The MPAA, for instance, never came into compliance. They just stopped distributing.
Or, at least, stopped distributing publicly. For all you know, they continue to distribute the toolkit in question privately, to people who don't bother asking for source.
That said, I did find the DMCA application in question highly satisfying. Thanks for that. :)
