Foveon sensor question?

Do any manufacturers besides Sigma use the Foveon sensor? It seems to be pretty amazing- the images I've seen are incredible. I understand that the Sigma cameras are not the greatest performers, but why aren't other four-thirds manufacturers using this sensor? Imagine taking the best of Leica, Panasonic, Olympus, and Fuji, and a Foveon sensor- isn't cross-compatibility what the four-thirds system is all about?

The only other consumer camera that uses a Foveon sensor is the Polaroid X530. The current generation of SLR Foveon sensors aren't 4/3rds sensors - they have a 1.7x crop factor, limiting the compatibility. Beyond that, a lot of the talk around Foveon's quality is pure hype - even magazines like Pop Photo have dismissed some of its claims and noted that there are instances where a camera like the Nikon D80 performs better in terms of color.

http://www.popphoto.com/cameras/4277/cam...
http://www.popphoto.com/howto/4276/foveo...

So far, the only company making 4/3 SLR cameras is Olympus. None of the other people who signed onto the 4/3 system are actually making SLRs that use 4/3 (although Sigma does make lenses in 4/3).

Sigma SLR cameras use the Sigma AF mount, which is very similar to a Canon EOS mount. It's not 4/3.

Besides Sigma SLRs, Sigma is also going to introduce their DP1 point and shoot with a Foveon sensor. And in the UK, a few Polaroids came out with a Foveon sensor before being recalled.

Fujifilm makes their own sensors (called the SuperCCD) and the others probably have a sensor supplier like Sony. They are unlikely to break long-standing agreements.

Ultimately, the 4/3 system is a technological dead end, because APS-sized and 35mm sized sensors, being physically larger, will inherently be less noisy and more efficient at gathering light. The top 3 SLR sellers are Nikon, Canon, and Pentax; Olympus is not making headway with their 4/3 system and there's no indications that things will get better for them.