Microsoft finally shows some support for open source, without any controversy or doubt hovering around it. As Matt Assay notes that the Windows Marketplace is hosting open source software. And this time it is open for all. The onus to put up the software there is on the software owner, so you might not find a lot of software there right now. Microsoft seems to realize that they have to promote Windows software, even the non-Microsoft ones, to truly help the Windows user. For the user, it is not always about Microsoft.
There are other popular sites which already do this, but an explicit market place might help Microsoft build a community of developers and users around it. I am not sure if Microsoft’s name gives more or less authority to the site, but by keeping it open to all it sure has the potential.