Google is adopting the BSD license for WebM in order to address a licensing conflict. When Google opened up the VP8 codec and announced the launch of the WebM project during the Google I/O conference last month, the actual license under which the code was distributed was not an official open source software license. It was a custom license that had not yet been approved by the Open Source Initiative (OSI), the organization responsible for maintaining the open source definition and validating licenses.

Google's custom license posed some problems because it included clauses that made it incompatible with GNU's General Public License (GPL), the most widely-used open source software license. It was a minor technicality, but one that would have broadly precluded adoption of WebM in many popular open source software applications. Fortunately, Google has rectified the conflict and has found an acceptable way to harmonize its licensing terms with the GPL.

As Google open source programs manager Chris DiBona explained in a blog entry today, the original license terminates the rights for downstream parties that bring patent litigation against Google. This basically means that any company that sues Google for patent infringement would lose the the right to redistribute WebM.

To avoid the resulting incompatibility with the GPL, Google decided to use a standard BSD license instead for the software copyright and draft a separate set of terms for the WebM patent grant.

"Using patent language borrowed from both the Apache and GPLv3 patent clauses, in this new iteration of the patent clause we've decoupled patents from copyright, thus preserving the pure BSD nature of the copyright license," wrote DiBona. "This means we are no longer creating a new open source copyright license, and the patent grant can exist on its own."

With the new approach, companies that sue Google for patent infringement have their rights to royalty-free use of the WebM patents terminated, but they do not lose the WebM source code distribution rights that are granted by the BSD license under copyright law. It basically has the same result as the original draft of the license, but it is structured in a way that is more practical in terms of license compatibility.