Citrix, a company that makes software for virtual workplaces, had been developing technology for Microsoft since the two struck a deal in 1997. Thursday's deal "is a logical next step," Bob Kruger, a Citrix product and development executive, said in a statement.
"This deal does not extend the 1997 agreement," he said. "Rather, it ensures that Citrix will continue to have access to new Windows releases in the future. It also demonstrates Microsoft's recognition of the value Citrix solutions add to Microsoft platforms."
Under the 1997 deal, Microsoft paid a one-time fee to use Citrix's technology. That agreement has not been renewed.
Citrix's software allows corporations to connect Windows and other operating systems to "thin clients" over a network. It works on top of Microsoft's Window Terminal Services (WTS) product, which is part of Windows 2000.
The company has posted strong financial results in the past few quarters, thanks in part to its relationship with Microsoft.
But rumors have surfaced that Microsoft might try tousing Citrix's technology in the future, either by buying a start-up or developing its own version. Thursday's announcement makes that seem even likelier.
Citrix Chief Executive Mark Templeton described the relationship as unilateral. "Citrix is licensing through Microsoft, Microsoft is not licensing from Citrix," he said.
The deal, which does not involve any financial terms, gives Citrix access for three years to current and future Microsoft operating systems, including Terminal Server interfaces.