We've seem "bounties" requested before a root, but not usually after root. In Rosenberg's case, he requested a $500 bounty before releasing the root, but only $200 would be for himself (for a Droid 4 of his own). The rest he would donate to charity.
After the uproar that ensued, he decided to donate all $500 to the American Red Cross, and has released the root, as well.
It's also the first step to installing a custom ROM. You can find the root (Windows) here. Put your Droid 4 into USB debugging mode, connect it to your PC, ensure you have the latest Motorola drivers installed, extract the entire zip file, and execute “run.bat."