The transaction actually involves Boeing purchasing Vought's South Carolina operation. That is where the 787 work is done. According to Vought's CEO, "the financial demands of this program are clearly growing beyond what a company our size can support."
So, Boeing will fork over $580 million, it will waive the requirement for Vought to repay money Boeing had already advanced the company in relation to the 787, and it also entered into new agreements with Vought regarding work on the rest of Boeing's commercial aircraft family. Sounds like a pretty sweet deal for Vought, because otherwise it sounds like they would have been facing some serious financial commitments.
For Boeing, this means they have more control over the production of the 787, they stabilize a large supplier for many other programs, and they potentially have the ability to start up a second production line if they so choose.