Under its controversial alliance with Novell, Microsoft is entitled to receive key technical documentation from the Linux distributor even if that documentation is not generally available to open source software developers, according to a Novell document.

Under the deal, Novell must provide to Microsoft documentation relating to the tools used to manage Novell's SUSE Linux operating system on virtual servers "whether or not Novell Management Interface Information is available publicly in the open source community," the document states.

While the arrangement may not technically run afoul of the open source General Public License, it's sure to irk Linux advocates who are already disgruntled with Novell for cozying up to their arch enemy.

Microsoft and Novell reached an accord in November under which Microsoft agreed not to press its patent claims over Linux against Novell's SUSE customers. In exchange, Microsoft won the right to re-sell Novell's Linux products and services at a markup.

Microsoft claims that Linux and other free software programs violate 235 of its patents.

In a filing with the Securities and Exchange Commission Friday, Novell revealed a number of new details about the Microsoft deal.

A copy of Novell's technical collaboration agreement with Microsoft attached to the filing shows that Novell must provide Microsoft with certain documentation related to running SUSE Linux virtually -- on an exclusive basis if necessary. "If any such Novell Management Information is not publicly available, it is provided for Microsoft's internal reference use only," the agreement states.

Virtualization is the process through which a single server is subdivided to run multiple operating systems. Large enterprises are increasingly implementing virtualization strategies in their data centers in an effort to reduce hardware needs, cut power consumption, and add flexibility.

The technical agreement shows the extent to which Microsoft is counting on its close relationship with Novell to add virtualization capabilities to its forthcoming Windows Longhorn Server product in an effort to match offerings by rivals EMC and IBM.

In addition to giving Microsoft first crack at some of Novell's virtualization management technology, Novell is allowed to use and create tools enabling SUSE Linux to run alongside Longhorn using Microsoft's application programming interface for virtualization.

Unlike some other vendors, however, Novell will be able to do so without fear of stepping on Microsoft patents. Any infringement actions that Microsoft might take against Novell in the future "shall not include any patent claims infringed by (i) any enabling technologies that may be necessary to make or use any Novell HyperCall API Implementation," according to the terms of the technical agreement.

It also calls for the two companies to develop protocols for testing Novell's virtual machine technology running on Microsoft's Viridian virtualization tool, which is expected to ship after the company releases Longhorn later this year or early next year. The catch: "Neither party will publicly release any test results without prior written consent of the other party," the collaboration agreement states.