<i>Well, what if I decide to make a toy web application that works with video and I decide to use HTML5 video standard?</i><p>Nobody is going to come after you. You're not even worth their time. Is it stupid that technically this may be interpreted as a possibility under law? Yes, but that's the stupid country we live in. The same thing could happen with Theora if someone claimed to hold a patent covering it, and you'd be equally screwed.<p><i>And what if I put the source code of this application on github or any other repository that's open to anyone?</i><p>No problems there.<p><i>And if I want to found a company that wants to make a living working with video online but nothing charging users directly, will I have to pay royalties only because every new user will expect that I should support the patented codec that he uses?</i><p>Talk to your lawyer. You're a company, right?<p><i>Now, what's about that's is open?</i><p>The standard is open. You are free to implement it. The licensing terms are open. You are free to license it. You are <i>not</i> free to distribute implementations to users without licensing the technology that has been <i>openly</i> provided.