So what’s the secret sauce? OpenStack, an open-source cloud-computing platform the company’s co-founder and CEO, Chris Kemp, helped develop at NASA. Nebula is also collaborating with Facebook’s Open Compute Project, an effort to open-source the social networking company’s server and data center technologies, in the hopes that cheaper hardware will enable more companies to deploy private clouds.

“Internet and gaming companies shouldn’t be the only ones with access to this technology,” says Kemp, former chief technology officer of IT at NASA. According to Kemp, companies are often faced with the choice of relying on public cloud infrastructure (a la Amazon’s (AMZN) Web Services), buying expensive, proprietary hardware and software or hiring a team of DIY technologists with the know-how to link together open-source technologies.

Palo Alto, Calif.-based Nebula hopes to offer a fourth option—what it says is a less costly (it won’t disclose the exact price) way to build a private cloud infrastructure, using its appliance which can be hooked up to thousands of inexpensive computers.

“If they execute well they have an opportunity to really fill a need,” says Frank Frankovsky, head of Facebook’s Open Compute Project. “And basing it [their product] on open source – both OpenStack and Open Compute—is unique.”

Why does Facebook care about private cloud deployments at other companies, including potential competitors?

It doesn’t. What it cares about is improving its own server, data center and storage hardware designs, making them run more efficiently in order to trim costs. In exchange for making its blueprints publicly available, Facebook is hoping other companies will contribute with their own innovations, open-source software style.

The social networking site generates a lot of buzz for new features and privacy controversies. Its less-sexy Open Compute Project, or the “open-sourcing” of its custom-built server and data center technology, made far less of a splash when it was unveiled last April. But over the last few months, the project has quietly made headway. Facebook says its community of contributors has grown to over 1,000. About 250 non-Facebook employees attended its first-ever Open Compute summit last month. The next one is scheduled for October, and you can bet Nebula will be there.

“Nebula has some very significant engineering talent,” says Facebook’s Frankovsky. “And they’ll actively contribute back.”

Nebula also has some very significant financial backers (again, the company won’t disclose the exact dollar amount it managed to raise). Its list of investors includes Sun Microsystems co-founder Andy Bechtolsheim and venture capital firm Kleiner Perkins Caufield & Byers. Five pilot customers from energy, finance, biotech and media industries will begin deploying private clouds using Nebula’s appliance in early October.

“Our business model is simple, you just buy a box and plug servers into it,” says Kemp. “We want to disrupt the existing economies here.”

Of course, while the use of open-source software and hardware could enable Nebula to offer a cheaper solution for private cloud deployments, the very definition of open-source technology means that it’s also available to any other company interested in utilizing it. Dell’s just-launched OpenStack Cloud Solution is also being touted as an alternative to existing cloud options that are based on proprietary, licensed software. And with both OpenStack and Facebook’s Open Compute Project still in their infancy, you can count on many more open-source cloud infrastructure “alternatives” hitting the market in coming years.