Although hosted by VMware, the twice-yearly VMworld has become one of the primary venues for vendors to display new virtualization technology. Even rivals Citrix and Microsoft maintain a presence at the show and have made the same week as VMworld.

The event’s neutrality seemed to be threatened when VMware modified its sponsor and exhibitor agreement, a change detailed in the , who writes about desktop and application virtualization.

Madden quotes the revised agreement as follows: “Sponsors and exhibitors must market or demonstrate products on the exhibition floor and in the sessions which are complementary to VMware products and technologies. Complementary products and services are defined as products/services that do not overlap/substitute with VMware's products/capabilities, and help expand the reach and solution scope of VMware's capabilities solely as deemed by VMware.”

Madden argued that this would effectively prevent competitors like Microsoft, Citrix, Neocleus and Virtual Computer from exhibiting at VMworld, which took place in Cannes, France in February and will be held in San Francisco in September.

VMware responded Thursday with a of its own, saying that it never intended to ban competitors and that in fact “Microsoft and Citrix have already signed up and will of course be participating in the conference this year, as well as hundreds of other companies.”