As Andi Gutmans mentions on his blog, the Zend Framework has reached the 10 million downloads mark and is still going strong:
When I started the Zend Framework project back in 2005 I was sure that we could make a difference. Some thought it was a long shot with too ambitious goals, after all I wanted to start from scratch without a single line of code, no community contributors and no corporate contributors. We are now 3.5 years later and I have to say Zend Framework's success has exceeded my own foresight and expectations.
He mentions the teams behind the Framework and some of Zend's partners that have helped to make it an amazing success.