Sure, IBM partnered up with Canonical this week to promote Ubuntu Linux and open source desktops against Windows 7. But Big Blue’s other big open source move — a growing relationship with Digium — has caught The VAR Guy’s attention. Here’s why. Fact is, desktops no longer sit at the center of the IT universe. VARs are looking for higher margin recurring revenue opportunities — many of which involve network-enabled applications. That’s where the IBM-Digium relationship enters the picture. Digium promotes Asterisk, the open source IP PBX that is turning heads in many IT departments.