Open source software company Red Hat believes that companies like VMware and Microsoft are skewing the definition of open cloud by claiming that their virtualisation products are open when in fact they are closed.

Speaking at a round table conference in London this week, Scott Crenshaw, head of Red Hat's Cloud Business Unit, said that several virtualisation vendors have started to claim they are open as a marketing gimmick.

“I've noticed that VMware has been joining a lot of consortiums with the word 'open' in the title,” said Crenshaw. “VMware's technical architecture reflects its business model, and that's lock-in. The day they open source their core virtualisation is the day that they can truly claim to be open.”

He added that VMware's recent decision to change its licensing model and charge per virtual machine has forced many IT executives to wake up to the necessity for open cloud, and realise that they do not want to be controlled by a single vendor.

Crenshaw also criticised Microsoft's approach of persuading customers to use one portion of its cloud technology and then “walking them into the complete stack”.

“Why would you ever lock yourself into a single vendor?” he said. “It doesn't give you a rich choice of which public clouds to run on, and it means cutting yourself off from innovation, unless that vendor happens to endorse it.”

Red Hat advocates the creation of open hybrid clouds that allow customers to build out their resources at the pace they want to, and replace any part of the stack with an alternative piece from another vendor. The company's Red Hat Enterprise Virtualisation (RHEV) and OpenShift platform-as-a-service (PaaS) products both adhere to this model.

Crenshaw said that open hybrid clouds provide users with the elasticity and self-service that they need, while providing IT departments with enterprise-class governance tools. However, he didn't take kindly to the suggestion that Red Hat is falling behind fellow Linux distributor Canonical in the enterprise sector.

“It may be selective data that they've put out, and it's their prerogative to turn the numbers the way they want,” he said. “When it comes to the heavy lifting, building serious scale clouds, spending hundreds of millions of dollars on proprietary software and making it open source, they are not anywhere in the same ballpark as Red Hat.”

Red Hat this week became the first open source software company to generate a billion dollars in annual revenue. Revenue was $1.13 billion, up 25% from the year earlier, and net income was $146.6 million, up from $107.3 million the year earlier.

"Red Hat's success is a testament to the role it played in bringing Linux to the mainstream, and the continued shift towards open source in the enterprise," said Mark Shuttleworth, founder of Canonical, in response to the news.