Similar to the bilda1 DAC, this version mostly existed as pictures on the linux-laser.org page. I believe it is a size-reduced implementation of the bIlda1 interface.
This was published at a time before there were really any USB DACs on the market. I'm only aware of kLaserPlay which is a Linux ILDA frame player/viewer based on the KDE desktop framework. Other software might support the interface, not sure.
There is a possibility that the RayComposerUSB DAC is the same as the webpage for RayComposerUSB answers at the linux-laser.org website.
Archive of the old linux-laser.org can be seen here: https://web.archive.org/web/20080314014033/http://www.linux-laser.org/
Pictures of the bIlda2 DAC: