gecko-dev/media/libvpx/PATENTS

Additional IP Rights Grant (Patents)
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"These implementations" means the copyrightable works that implement the WebM
codecs distributed by Google as part of the WebM Project.

Google hereby grants to you a perpetual, worldwide, non-exclusive, no-charge,
royalty-free, irrevocable (except as stated in this section) patent license to
make, have made, use, offer to sell, sell, import, transfer, and otherwise
run, modify and propagate the contents of these implementations of WebM, where
such license applies only to those patent claims, both currently owned by
Google and acquired in the future, licensable by Google that are necessarily
infringed by these implementations of WebM. This grant does not include claims
that would be infringed only as a consequence of further modification of these
implementations. If you or your agent or exclusive licensee institute or order
or agree to the institution of patent litigation or any other patent
enforcement activity against any entity (including a cross-claim or
counterclaim in a lawsuit) alleging that any of these implementations of WebM
or any code incorporated within any of these implementations of WebM
constitute direct or contributory patent infringement, or inducement of
patent infringement, then any patent rights granted to you under this License
for these implementations of WebM shall terminate as of the date such
litigation is filed.