In what a company executive called a "pretty radical upgrade" and "the biggest release in our history," Six Apart today released a free beta of its Movable Type 4.0 (MT4) blogging platform. The San Francisco company also announced plans to release the first open source version of its popular Movable Type blogging software this summer.

Along with a major change to its interface and a focus on ease-of-use, MT4 includes more than 50 new features. Among those features are more powerful template management tools to speed site development, an installation and upgrade wizard and new themes designed to help users create an attractive blog within minutes.

For enterprise management, MT4 enables the management of multiple blogs and many users in a central interface. An aggregator feature pulls multiple blogs into a single blog.

The upgrade itself represents a new direction in how Six Apart will evolve the product line. Instead of a separate enterprise version, there will be one version and functional "packs" for different corporate needs.

"Now all our development on the platform can go in one product, we don't need to bloat it with enterprise capabilities not everyone needs," Chris Alden, executive vice president at Six Apart, told internetnews.com.

Six Apart said MT4 has enough tools and features for customers to build full Web sites that can be managed and updated at a fraction of the cost of traditional content management systems.

The software's new content and asset management tools are designed to make uploading and revising photos, documents and videos easy. Also, users can create standalone Web pages that automatically inherit the design of the blog for a consistent look and feel.

"We're not going after Vignette and the others big CMS providers, but there's a market for those who want a little more than a blog but not as much as a big CMS," said Alden. He noted customers such as Reed Business have used Moveable Type to create "micro sites" for trade publications that didn't have an accompanying Web site.

While Six Apart continues to encourage and support what Alden calls the traditional "personal punditry" that blogging is known for, he sees a growing corporate acceptance in blogging for productivity.

"We've had CIOs tell us we don’t want to be irrelevant to an entire generation of workers," said Alden. "A new employee gets an e-mail address, but if they're under 25 it's not the way they're used to communicating."

Six Apart bills itself as the world's leading independent blogging software and services company. Customer include Boeing, Genentech, Oracle, WalMart, USA Today and NBC Universal.

On the open source front, Six Apart has been a major contributor with its other products and technology, such as LiveJournal and Mecached database caching. Now Six Apart plans to add MT as part of a dual-license strategy that will include continued commercial licensing and the new open source version due out later this summer.

Separately, Six Apart will announce a number of new features to its hosted blogging service, TypePad, later this week.