I found on eBay, a guy telling that he will sell a server (Intel based) with the Raq550 OS ... Is it possible to do that?
Sure it's possible. Now that the code's been released under a BSD license, it shouldn't be a violation of the License Agreement on the OSRCD.
There's a project at http://open.cobaltqube.org/ that describes how to load the Qube stuff on a PC. I'm sure the 550 OS isn't much different.