Theora

• FOURCC: ???
• Company: Xiph
• Samples: http://samples.mplayerhq.hu/V-codecs/Theora/
• Patents: On2 claims to hold several (undisclosed) patents, but has granted an irrevocable, royalty-free, transferrable license for any use, distribution, or sale of their VP3 software, or any derivative thereof (including Theora). It is unclear which patents actually apply.
• Website: http://theora.org
• Theora at XiphWiki

Video codec developed by Xiph. Theora is based on VP3, which On2 released as open source.