In what appears to be an effort to diminish the appeal of the WebM project backed by Google, Mozilla, and Opera, among others, MPEG LA, a group that manages pools of patents on behalf of participating companies, on Thursday declared that its AVC Patent Portfolio License will continue to be free to licensees who deliver Internet video for free to end users for the life of the License.

Licensees who deliver paid Internet video will continue to have to pay a license fee.

The AVC Patent Portfolio covers the H.264 video codec. It is licensed on behalf of 27 companies including Apple and Microsoft, both of which support H.264 in their media software and browsers. Organizations that support open source software, such as Mozilla, however, refuse to support H.264 for fear of future licensing fees.

MPEG LA said in February that it would not charge royalties for the AVC Patent Portfolio from January 1, 2011 to December 31, 2015.

That deal began to look less generous in May, when Google released the VP8 video codec, obtained in its acquisition of On2, as royalty free, open-source software and launched the WebM project with various partners for the purpose of promoting an open media format for the Web.

But promising to license H.264 at no charge isn't enough to convince Mike Shaver, VP of engineering at Mozilla, to embrace the technology.

"The MPEG LA announcement doesn't change anything for the next four years, since this promise was already made through 2014," Shaver said in an e-mail. "Given that IEC [International Electrotechnical Commission] has already started accepting submissions for patents in the replacement H.265 standard, and the rise of unencumbered formats like WebM, it is not clear if H.264 will still be relevant in 2014."

Google did not respond to a request for comment.

MPEG LA CEO Larry Horn wasn't immediately available for comment.

Asked about MPEG LA's rationale for the change in license pricing, a spokeperson for the group said in an e-mail, "This is a decision of the patent holders based on their general sense that this clarification is beneficial to the market in responding to its demand for AVC deployment."

Several months ago, Horn claimed that some of his group's patent holders held patents that covered Ogg Theora, an open source codec favored by Mozilla.

Apple CEO Steve Jobs appears to have gone further in an e-mail by claiming, "A patent pool is being assembled to go after Theora and other 'open source' codecs now."

To date, no such lawsuit has surfaced. But given the legal wrangling between Apple, Google, Oracle, Nokia, and just about everyone else in the mobile arena, it would hardly be surprising to see further litigation.

Update: Updated story to clarify that licensees serving paid video are unaffected by this change.