Shuttleworth proposed the delay last week.
In explaining the delay, he said Monday, "The extra time will help ensure that Dapper is a robust and reliable platform for organizations with long-term and large-scale free software deployments. This is the first release of Ubuntu that will be supported for 5 years on the server and 3 years on the desktop, and we believe that this release will help expand the reach of the Ubuntu and Debian communities substantially."
Though Dapper Drake was delayed, its as yet unnamed sequel is still expected in October, he added.
The news came shortly before Microsoft delayed its own next-generation Windows operating system, Vista.