The PFIF is paying $15,000 for the documentation.
The practical impact is that Microsoft can no longer "break" Samba by changing protocol formats. Samba enables Linux servers to exchange data with Windows servers, and is distributed under the GPL.
The ongoing fear for Samba was that, since it translates data into Microsoft formats, Microsoft might go after it in court for infringing on its patents. That fear is no more.
Andrew Tridgell of Google, who is the original developer of Samba, and Eben Moglen of the Software Freedom Law Center, who set up the PFIF, both helped negotiate the deal.
It's important to note that the interoperability code is not being made public. It is merely being transferred, via the PFIF, to the Samba project.
You might think of this as Eben's Christmas present to the community. His beard gets more like St. Nick's every year!