Cloud computing has progressed on multiple fronts over the past week, and one of the most interesting advances is the fact that Microsoft has decided to support the open source project Open Stack.

OpenStack, you may remember, was the joint project announced by Rackspace and NASA in July 2009 to produce a suite of open source software to equip a cloud service provider with a standard set of services. It's likely to be adopted by young cloud service providers and some enterprises.

Microsoft offers its own Azure cloud, and it hopes plenty of Windows users gravitate to its cloud services. But just in case not everyone does, it's commissioned startup Cloud.com, a supplier of cloud software, to provide support for Hyper-V in the OpenStack set of software. Cloud.com builds a variant of OpenStack, called CloudStack, which it offers to the demanding large-scale service provider market.

Tata Consulting's cloud services are based on CloudStack, as is Korea Telecom, Logixworks, Profitability.net, Activa.com, and Instance Cloud Computing. CloudStack is open source code issued under GPL v3.

I sat down recently with Peder Ulander, CMO of Cloud.com, to ask about what his firm was doing for Microsoft and Hyper-V. OpenStack was announced as providing infrastructure software for a cloud environment that would run open source hypervisors Xen and KVM. By Xen, he also means XenServer from Citrix Systems, a commercial implementation.

By giving OpenStack the ability to host Hyper-V hypervisors as well, it will broaden the opportunity to build clouds with the project's open source code, he noted.

"Right now, clouds are architected for each environment," he said. That means Amazon Web Services' EC2 runs Amazon Machine Images, a proprietary variation of the Xen hypervisor.

Likewise, since its virtual machines don't run in EC2, VMware has been busy equipping services providers with cloud infrastructures that run its virtual machines. AT&T's Synaptic Compute Cloud, Bluelock, and Verizon Business are vCloud data centers running workloads under the VMware ESX hypervisor.

OpenStack, and its commercial implementers, such as Cloud.com, are trying to broaden the playing field. One open source stack able to run workloads from a variety of hypervisors might prove more viable than the present trend of creating hypervisor-specific cloud services, Ulander said.

By integrating support for Hyper-V operations into OpenStack, the open source project will multiply the potential number of users of cloud services built on open stack, and hopefully, its number of adopters.

Microsoft contributed code to Cloud.com, which in turn performed the integration into OpenStack, he said. Ted McLean, general manager of Microsoft's open solutions group, said in information posted on Microsoft's website that the contribution through Cloud.com to OpenStack was consistent with Microsoft's view that its customers operate heterogeneous environments and will use more than one hypervisor and cloud service.

Citrix's Simon Crosby, trailing painfully behind VMware in the virtualization market and never one to mince words anyway, said in a blog: "Across the board, service providers and enterprises have told us that they are not enthusiastic about a monolithic, single vendor cloud stack that by definition makes all clouds identical."

OpenStack organizers are geared toward satisfying the needs of future cloud service providers, who will need to scale out to large numbers of users. However, the OpenStack code is likely to be picked up by some enterprises, particularly those with large numbers of employees, Ulander said. But smaller enterprise needs are not the primary focus of the project.

The Eucalyptus cloud stack has a different focus from OpenStack. It provides a cloud infrastructure for the enterprise that is compatible with Amazon's EC2. Its open source APIs are capable of invoking EC2 services, such as S3.

Another project, Simple API, backed by Zend Technologies, Microsoft, IBM, and others, offers APIs to connect with cloud services that developers may build into their applications. Cloud vendors who support the APIs will find their services work with the applications.

Open source code is providing several avenues into the cloud. But Microsoft's support of OpenStack gives it a lift amidst a crowded field.