Microsoft to contribute to Joomla. Oh no.

Via The Register, I came across a link to a blog article (Microsoft Contributing More to OSS | Josh Holmes) enthusing about a move by Microsoft permitting its employees to contribute to the open source CMS Joomla!. [Edit: Josh Holmes is a Microsoft employee, so one might expect him to be enthusiastic about this development]. This interests me since this site (and about three others that I run) are constructed using the Joomla! CMS.  There's also an announcement on the Joomla! site (Microsoft signs the Joomla! Contributor Agreement):
Microsoft has signed the JCA (Joomla! Contributor Agreement), and we've got some of their code in the Joomla! 1.6 trunk. There, I said it. It feels like it should be so much more doesn't it? Don't worry, I won't end the blog post there.
I'm sorry. but I don't share the enthusiasm of these two articles (and nor do many of the commenters).  Microsoft is a very dangerous company to get into bed with, and its track record on open source software is not glittering. Remember Microsoft's strategy: Embrace, Extend, Extinguish. I'm not about to re-version my websites just yet.  But I'm going to start thinking how to move them to another platform that's not associated with Microsoft so I'm ready when the shit hits the fan.  Perhaps Drupal beckons. Update: Mary-Jo Foley over at ZDnet says (Microsoft signs agreement to contribute to Joomla open-source project)
In an April 27 post to the Joomla Community Portal site, the Joomla team noted that some of Microsoft’s code is in the Joomla 1.6 trunk. About half the commentors on the Joomla site were upbeat about Microsoft’s involvement in Joomla, noting that the Redmondians have been sponsoring many PHP events, as of late. But the other half were skeptical of Microsoft’s interest and involvement in open-source in general, and Joomla, in particular. Microsoft has been working on its own open-source CMS platform, codenamed “Orchard.” Microsoft recently transferred responsibility for Orchard to the CodePlex Foundation, and a handful of Microsoft employees working on Orchard have been assigned full-time to the Foundation for three years. Microsoft also has its own paid CMS platform in SharePoint Server.
Doesn't this worry the Joomla! guys?