Mozilla has finally accepted Microsoft's offer of help towards ensuring interoperability between Firefox and the upcoming Vista operating system.

Microsoft had offered Mozilla help Microsoft offered to open up a new open source facility at its headquarters in Redmond to Mozilla software engineers, including giving them one-on-one time with Microsoft people. The offer includes help with the Thunderbird email client.

In reply, Mike Beltzner, a "phenomenologist" for Mozilla and the company's spokesman on this issue, said: "Yes, we'd definitely be interested in getting some one-to-one support".

But Beltzner pointed out that Mozilla had already "been testing on Vista" with Firefox and Thunderbird "as well as working to ensure that we take advantage of the new 'Default Program' infrastructure".

Default Program is a new feature Microsoft has added to Vista to avoid the problem of applications taking over common functions, such as playing music or browsing the Web, from each other. Rather than letting competing applications fight, it will give the user a single interface for deciding which programs should do which jobs. More details are available on this document, released by the Microsoft Windows Application Experience Group earlier this month.

Beltzner also warned that one of the main issues for Mozilla was support for third-party software developers. "Do you know if there are any spots for other open source groups that are using Firefox/XULRunner as a platform such as Songbird and Democracy, or Flock?" Beltzner asked.

"Something like a checklist of the most common OS integration points that have changed from Windows XP would be extremely useful," he pointed out, adding that it's important that this is "accessible to organisations that can't afford to send people to Redmond".

Both Microsoft and Mozilla appear keen to bury the idea that the two are warring tribes when it comes to open source. This recent move by Microsoft to openly welcome Mozilla and its browser, even though Firefox is the principle competition for its own Internet Explorer, appears to be part of a new trend for the company.