They're dropping like flies to OpenStack's siren song.

The open source cloud platform's latest conquest is EMC, whose VMware subsidiary already did a seemingly unthinkable thing a few months ago and joined the rival band as a gold member.

EMC is only joining as a corporate-level sponsor.

To explain why EMC, a born street fighter, would tie up at all with a movement pledged to destroy VMware, the company wheeled out its global marketing CTO Chuck Hollis who blogged that OpenStack is catching on like Linux did and even though it may still be immature customers are asking about it.

"Over the last year," he wrote, "we've been informally talking with customers and partners about their interest in OpenStack. The surprising thing is just how much serious interest has emerged in the last six months or so. It's gone from a small handful of devotees to a much larger crowd of enterprise IT shops and IT service providers who now have the technology on their roadmap in one form or another. To be sure, everyone has their eyes open around the current state of maturity in the various distributions. Nobody seems to think it's a shrink-wrap bulletproof experience these days - indeed, most people using the environment today are doing a fair bit of coding :). But you can see where it's going."

So EMC is going to bend to demand and support the stuff, join the key projects and communities, contribute and invest in specific interfaces relevant to its storage business such as Cinder. It means to hone in on a handful of popular distros, and make sure they're qualified and supported, and that its value-add works well in these environments....

"Over time," Hollis said, "we believe that OpenStack-based distributions will be considered by more IT organizations - just like Linux before it. The per-customer specifics will vary widely based on all sorts of factors, but it's hard to argue the macro trend."

And "the OpenStack Foundation is the key industry nexus point for the evolution of a growing number of different-flavored distributions and editions."

Amazon and Microsoft have not joined.