I wrote about something similar with VP8, which is highly patent-encumbered. Google was like:

1. You have a license to our related patents

2. You're on your own if someone else claims that your use of our stuff infringes their patents

    2a. But if the party suing is also a licensee, they lose their license.

3. You lose your license if you come after us for anything.

These kinds of licenses have network effects, and are only really effective in a mutually-assured destruction scenario.

http://ipjournal.law.wfu.edu/2011/03/googles-afraid-its-free...