umbraco is an open source project with roots back to year 2000 even though it wasn't released as open source until 2004. Prior to that it was founder Niels Hartvig's home-grown weapon of choise for working as a freelancer.
Today it has grown to be among the top fifteen most popular open source .NET applications and in April 2007 we hit a milestone at 25.000 installed websites.
umbraco is a registered trademark of Niels Hartvig