Microsoft said Wednesday that it has expanded a partnership with Novell under which it purchases certificates for Novell Linux support and resells them to customers at a markup.

As part of the revised arrangement, Microsoft will purchase up to $100 million worth of certificates, beginning November 1. The investment is in addition to the $240 million in Novell Linux certificates that Microsoft agreed to purchase when the companies first struck their alliance in November, 2006.

Microsoft said that Novell has invoiced more than $157 million in certificate revenues, or 65% of the initial allotment, since the deal was originally signed.

Microsoft also said that it would work with Novell to develop new tools and services aimed at helping customers deploy Windows and Linux side-by-side, a setup that's becoming increasingly common in enterprise datacenters. "The collaboration between Microsoft and Novell has been built on our desire to meet our customers' real-life IT requirements," said Microsoft chief operating officer Kevin Turner, in a statement.

"Some customers have told us they want to be able to run Windows Server and Linux together seamlessly, but in many cases, they need help with the transition to (Novell's) SUSE Linux Enterprise Server from other Linux environments," Turner added.

Microsoft has long claimed that Linux violates a number of its Windows OS patents, but has said that it would indemnify Linux users from any possible legal action as long as they use distributions of the open source operating system from Novell or other distributors with which it has formal partnerships.

The open source community insists that Linux does not step on any patents and has challenged Microsoft to name the specific patents it believes have been violated. The company, to date, has declined to do so.