The UL - United Linux - initiative is directed towards using Linux in business environments mostly. The aim is to set a quasi standard for developers. Certifiability is another goal of the Group. Support comes from giants like IBM or SUN. The initiative said it already invited Redhat and other distributors to join.
The whitepaper on the groups site makes for an interesting read: www.unitedlinux.com/en/whitepapers/misc/whitepaper_ul.pdf
They mentioned that they invited redhat to join, but I think they new full well that redhat would refuse.
The four distros mentioned are RPM based, they are also relatively small compared to the girth of Redhat. From a business perspective I see this as a way that these four smaller vendors cold chip away at redhat dominance.
I can't see distributions like gentoo, slackware, and debian jumping on board.
I think it is a good idea, but I really just see it as a way to develop a standard that is not redhat, a way to combine market shares to collectively tackle the big kid in the playground.