Google is complaining about Microsoft. I still can't setup a multiuser (group) chat using a pidigin. It's only available to google talk gadget users.
I went to my neighbor's house for a birthday get together. Everybody there had a Yahoo! account and no one wants them to be bought by Microsoft. Some of these people were over 70 years old. What does that tell you about Microsoft's credibility?
Zimbra users are concerned about the Microsoft offer to purchase Yahoo!. Zimbra is an Exchange competitor. It uses a pseudo opensource license that is similar to Mozilla's. It requires attribution. It is possible to fork it, but whom ever does will have to put a powered by Zimbra notice at the bottom of the web pages served.