Microsoft is more open -- at least on the surface -- and that's all that matters in the cloud era, one company exec maintains.

At Oscon 2011, Gianugo Rabellino, Senior Director for Open Source Communities at Microsoft, said as long as the APIs, protocols and standards for the cloud are open, that is, open surface, customers don't care about the underlying platform.

So, it does not matter that the cloud is built primarily on open source technologies, notably Linux?

"Am I saying that openness doesn't matter in the cloud? No, openness is extremely important [but] I argue that in the cloud the source code is the Terms of Use and the SLA," Rabellino said, referring to service-level agreements."

He coined these terms -- open surface and open core -- to describe a continued commingling -- or a blurring -- of open source and closed source software that lies at the core of the enterprise and the cloud.

Open core, or open source, is the existing model in which core features are open source and value-added proprietary commercial software is built on top of it to monetize the technology.

The open surface model, Microsoft's approach, can be done with APIs, protocols and standards, the Microsoft exec said. The two models are coming together nicely.

He noted, for example, that PHP and Red Hat Enterprise Linux 6 run on Microsoft's Azure cloud platform "pretty well" and that Microsoft is working with WordPress, Drupal, Zoomla, Eclipse and other open source projects to ensure interoperability on Azure.****

"This is what's happening in the cloud. the cloud changes a lot of things. the [traditional] yardsticks we had aren't there anymore. What version of Facebook are you running? it doesn't matter anymore," he noted. "In the cloud, you have all this technology blurring . Sometimes you don't see them and when you see services , does it matter? Can you tell what stack has been producing JSON or XML feed? No."

Microsoft also announced a new version of Azure SDK for PHP is now available and the company is announcing new tools to cloud enable open source developed applications for Azure. The company is also working with almost 400 open source projects to ensure interoperability, including an open source project called PHP Cloud Sniffer.

Rabellino, who came to Microsoft from Italy nine months ago, said employees in more than half of Microsoft's 60 buildings in Seattle are working with open source projects.

"We have changed as a company. We have become more open. We want to work with open source comunities," he said.

Microsoft is a Diamond sponsor of OSCON 2011.

****CORRECTION: Actually, it's PHP and Java that run well on Azure. Microsoft has said it will support Red Hat Enterprise Linux 6 on Hyper-V. I regret the errors.