This comment in response to that post makes an interesting point; the most similar bits are likely the most carefully vetted, and may be written deliberately to avoid patent infringement. Patents on standards can be very narrow; as long they cover exactly what's in the spec, then any implementer of the standard still has to pay up:

"Patents are about _details_ so the mere fact that something does something like something else, isn’t necessarily something at all.

As we’ve pointed out before, many codec patents are exceptionally easy to work around: They specify every little detail because it makes it _much_ easier to get through the examination but doesn’t harm the patent’s ability to read on the final standard because the standard specifics exactly the patented behaviour.

D_S, for all his undeniable H.264 experience isn’t an expert on patents or even the H.264 patents. We can assume that in cases where VP8 looks similar to H.264 those would have been exactly the cases where care was taken to differ in the right places. I’d expect the primary risks for VP8 to be anywhere _but_ there."

more at http://blog.gingertech.net/2010/05/20/vp8-adobe-is-the-key-t...