Ah, the gloves are coming off. VMware, under the guise of a proprietary virtualization company, is inching up the software stack to horn in on Microsoft's prized Office turf, a piece of ground well known to its CEO, ex-Microsoft nabob Paul Maritz.

It's bought SlideRocket, a five-year-old San Francisco SaaS-based business presentation ISV that leverages cloud computing, collaboration, social media and mobile computing platforms, giving it a practically perfect checklist score, especially if you throw in the fact that, in keeping with the custom of the day, it gives its entry-level widgetry away for free.

This checklist paradigm claims more than 20,000 customers and 300,000 users, a base it's built up since its software left beta in October of 2008. In that space of time it says its widgetry was used to produce 10 million presentations.

VMware observes that presentation software - to wit the "25-year-old" PowerPoint - is second only to e-mail as the most widely used business tool. And VMware's already got Zimbra's open source e-mail and collaboration software from Yahoo, an application ornament that, like SlideRocket, is evidently supposed to advance its scheme whatever it is.

It also just took over Mozy, the consumer online backup operation, from its parent company EMC, and went into the Platform-as-a-Service business a couple of weeks ago with an open source thing called Cloud Foundry for building applications that run and scale in the cloud, anybody's cloud, public or private.

The Cloud Foundry move pushed Gartner VP Chris Wolf to remark that "VMware can't remain primarily as a platform for Windows applications in an area where Microsoft is a direct competitor. That story always ends the same." Like a lot of other people he's just not sure, when all is said and done, if VMware will be an enabler or a provider.

Perhaps it will be clearer what VMware wants to be when it grows up when it releases its reported Project Horizon applications portal and management widgetry in a few weeks. It's eventually supposed to handle both on-premise and cloud apps.

VMware said the SlideRocket acquisition would advance its vision of leveraging cloud computing "to deliver access to applications and data from any device, where and when a user needs it" and "help VMware drive a new model for end-user computing for the enterprise."

It claims SlideRocket offers distinct advantages that separate it from who-know-who's "legacy PC-era presentation technologies" such as:

• Online authoring, editing and access combined with built-in collaboration and version control allowing simultaneous team-based authoring while preserving a single consistent file
• An intuitive web-based interface for incorporating video, audio, photos and transitions and quickly assembling rich dynamic presentations
• Dynamic data feeds from sources like Google, Twitter, Salesforce and financial services to create charts and graphs, social network feeds and embedded financial data that are up-to-date and real-time
• Shared access, both online and offline, across a range of end-user devices, from desktops to mobile devices and tablets
• A centralized shared content library that speeds design time and drives consistency across organizations
• Unique real-time viewer feedback and analytics to capture key usage metrics, provide insight into presentation effectiveness and continually improve content

Naturally there's also the inevitable SlideRocket Marketplace for browsing and purchasing content including themes, stock photography, graphics, data feeds, audio, video, illustrations, animations and plug-ins. And naturally there are browser-based tools for creating new presentations. And lest users worry about losing their historic investment in PowerPoint slides, they can be imported into the SlideRocket environment.

It's not clear yet what, if anything, VMware is going to do about the fact that SlideRocket uses Amazon S3 to store its customers' physical files.

Terms were not disclosed. SlideRocket raised $7 million in venture funding from Hummer Winblad and Azure Capital Partners. It sells its Pro version for up to 25 users for $24 a user a month. Its enterprise edition for up to 50 users requires a call to the company. The enterprise version is supposed to have enterprise-grade analytics.