Why Microsoft is Going Open Source

All is explained here (well, not all, but a bit.)

Microsoft Goes (a Bit More) Open Source

Many people were amazed back in 2004 when Microsoft released its first open source software, Windows Installer XML (WiX). But this was only the first step in a long journey towardness openness that Microsoft is making - and must make - for some time to come.

It must make it because the the traditional way of writing software simply doesn't work for the ever-more complex, ever-more delayed projects that Microsoft is engaged upon: Brooks' Law, which states that "Adding manpower to a late software project makes it later," will see to this if nothing else does.

Microsoft itself has finally recognised this. According to another fine story from Mary Jo Foley, who frequently seems to know more about what's happening in the company than Bill Gates does:

Beta testing has been the cornerstone of the software development process for Microsoft and most other commercial software makers for as long as they've been writing software. But if certain powers-that-be in Redmond have their way, betas may soon be a thing of the past for Microsoft, its partners and its customers.

The alternative is to adopt a more fluid approach that is a commonplace in the open source world:

Open source turned the traditional software development paradigm on its head. In the open source world, testers receive frequent builds of products under development. Their recommendations and suggestions typically find their way more quickly into developing products. And the developer community is considered as important to writing quality code as are the "experts" shepherding the process.

One approach to mitigating the effects of Brooks' Law is to change the fashion in which the program is tested. Instead of doing this in a formal way with a few official betas - which tend to slow down the development process - the open source method allows users to make comments earlier and more frequently on multiple builds as they are created, and without hindering the day-to-day working of developers, who are no longer held hostage by artificial beta deadlines that become ends in themselves rather than means.