Sun and Microsoft’s icebreaking partnership finalized in the wee hours of Friday morning could provide years of relief from agonizing integration projects for corporate IT if the marriage turns out as solid in real life as it looks on paper.

The 10-year partnership between the two bitter rivals promises to improve interoperability between Sun and Microsoft servers and between Microsoft clients and Sun servers through what the pair call a Technical Collaboration Agreement to share proprietary technology. The two also plan to collaborate closely on Java and .Net.

The biggest benefits for IT would be the ability to mix and match network infrastructure and the opportunity to potentially mix run-time environments for applications written in either Java or .Net.

Those benefits will only come if the relationship goes as smoothly as the joking and bantering at a press conference early Friday between CEO’s Scott McNealy of Sun and his counterpart at Microsoft, Steve Ballmer. The two Michigan natives exchanged autographed Detroit Red Wings hockey jerseys as peace offering after years of acrimony between the two companies.

The greatest short-term IT benefit likely will be for Microsoft customers facing a September 2004 deadline for end-of-support on the Microsoft Java Virtual Machine.

The development is a limited lifeline for companies with legacy applications that require the Microsoft JVM and its Microsoft specific extensions that fostered legal trouble with Sun.

Sun sued Microsoft in 1997 for improper use of Sun’s Java technology, and the pair settled in 2001, with Microsoft paying $20 million and agreeing to phase out its JVM product at the heart of the suit.

“Today’s agreement gives us a guarantee for a three-year period [to support the Microsoft JVM] with the ability to extend beyond that,” says Mary Snapp, vice president and deputy general counsel for Microsoft.  She says the extended support will cover bug fixes, security vulnerabilities and other issues, but will not include any further development or inclusion in future products.

“At some point that Microsoft JVM has to go away, but we did not want to create a huge problem for our customers,” says John Fowler, CTO for software at Sun.

Another problem area for which IT should see some relief is with identity management and messaging/collaboration software.