37Signals does not belong on that list (Score 1)

Jive, SugarCRM, and Novell are all companies that are built around products that are open source. While 37Signals has released an application framework as open source, their applications, like Backpack, Basecamp, and Highrise are not open source. 37Signals is a great company with really good products, but I don't think they are the sort of company that Ballmer was referring to.