Citrix contributing CloudStack to the Apache Software Foundation isn’t so much a shot at OpenStack (it just happens to get caught in the crossfire), as it’s a shot against VMware.

There are two primary ecosystems developing in the world: VMware and Amazon. Other possibilities, like Microsoft and OpenStack, are completely secondary to those two. You can think of VMware as “cloud-out” and Amazon as “cloud-in” approaches.

In the VMware world, you move your data center (with its legacy applications) into the modern era with virtualization, and then you build a private cloud on top of that virtualized infrastructure; to get additional capacity, business agility, and so forth, you add external cloud IaaS, and hopefully do so with a VMware-virtualized provider (and, they hope, specifically a vCloud provider who has adopted the stack all the way up to vCloud Director).

In the Amazon world, you build and launch new applications directly onto cloud IaaS. Then, as you get to scale and a significant amount of steady-state capacity, you pull workloads back into your own data center, where you have Amazon-API-compatible infrastructure. Because you have a common API and set of tools across both, where to place your workloads is largely a matter of economics (assuming that you’re not using AWS capabilities beyond EC2, S3, and EBS). You can develop and test internally or externally, though if you intend to run production on AWS, you have to take its availability and performance characteristics into account when you do your application architecture. You might also adopt this strategy for disaster recovery.

While CloudStack has been an important CMP option for service providers — notably competing against the vCloud stack, OnApp, Hexagrid, and OpenStack — in the end, these providers are almost a decoration to the Amazon ecosystem. They’re mostly successful competing in places that Amazon doesn’t play — in countries where Amazon doesn’t have a data center, in the managed services / hosting space, in the hypervisor-neutral space (Amazon-style clouds built on top of VMware’s hypervisor, more specifically), and in a higher-performance, higher-availability market.

Where CloudStack has been more interesting is in its use to be a “cloud-in” platform for organizations who are using AWS in a significant fashion, and who want their own private cloud that’s compatible with it. Eucalyptus fills this niche as well, although Eucalyptus customers tend to be smaller and Eucalyptus tends to compete in the general private-cloud-builder CMP space targeted at enterprises — against the vCloud stack, Abiquo, HP CloudSystem, BMC Cloud Lifecycle Manager, CA’s 3Tera AppLogic, and so on. CloudStack tends to be used by bigger organizations; while it’s in the general CMP competitive space, enterprises that evaluate it are more likely to be also evaluating, say, Nimbula and OpenStack.

CloudStack has firmly aligned itself with the Amazon ecosystem. But OpenStack is an interesting case of an organization caught in the middle. Its service provider supporters are fundamentally interested in competing against AWS (far more so than with the VMware-based cloud providers, at least in terms of whatever service they’re building on top of OpenStack). Many of its vendor contributors are afraid of a VMware-centric world (especially as VMware moves from virtualizing compute to also virtualizing storage and networks), but just as importantly they’re afraid of a world in which AWS becomes the primary way that businesses buy infrastructure. It is to their advantage to have at least one additional successful widely-adopted CMP in the market, and at least one service provider successfully competing strongly against AWS. Yet AWS has established itself as a de facto standard for cloud APIs and for the way that a service “should” be designed. (This is why OpenStack has an aptly named “Nova Feature Parity Team” playing catch-up to AWS, after all, and why debates about the API continue in the OpenStack community.)

But make no mistake about it. This is not about scrappy free open-source upstarts trying to upset an established vendor ecosystem. This is a war between vendors. As Simon Wardley put it, beware of geeks bearing gifts. CloudStack is Citrix’s effort to take on VMware and enlist the rest of the vendor community in doing so. OpenStack is an effort on the part of multiple vendors — notably Rackspace and HP — to pool their engineering efforts in order to take on Amazon. There’s no altruism here, and it’s not coincidental that the committers to the projects have an explicit and direct commercial interest — they are people working full-time for vendors, contributing as employees of those vendors, and by and large not individuals contributing for fun.

So it really comes down to this: Who can innovate more quickly, and choose the right ways to innovate that will drive customer adoption?

Ladies and gentlemen, place your bets.