In the early 1990s Westerfeld joined a startup gaming company named Stardock where he was deeply involved in developing Object Desktop for OS/2. He contributed to the Microsoft Windows follow-on product, ObjectDesktop.NET. Theo Mandel acknowledged his contributions in his 1997 book, The Elements of User Interface Design. In 1997 the OS/2 market began to decline. Westerfeld left Stardock to work at Managed Objects in 1998 where he was named co-chief technology officer in 2002. In 2009 he filed three patents relating to "social networks and communities". He has three children.