One reason there may not be much movement around the open Prometheus PCI is that the current firmware is pretty limited and lacks PCI to PCI DMA. I know Michael Böhmer developed a newer version with this capability. I've heard a few people have gotten their Prometheus cards upgraded. If that firmware was released more widely I think there would be some renewed interest. In theory that was going to happen at some point as can be seen here:
http://www.e3b.de/prometheus/ Sadly, this was from some time ago so I don't think it is going to happen.
