Before the channel was sold to Desmond in July for £103.5m previous owner RTL decided to pull out of the joint venture with the BBC, ITV, C4, Talk Talk and Arqiva.
But now Channel 5 is back on board, with Desmond saying the web-based video-on-demand service is "set to shape the future of broadcasting".
"It will open up new and exciting possibilities for viewers," says Desmond. "This is important to the future of Channel 5 and having an open internet-connected TV platform fits closely with our plans to bring brilliant new content and interactive services to viewers.
"We're delighted to renew Channel 5's commitment to supporting Project Canvas following a review of our digital strategy."
The BBC Trust approved Project Canvas in June, despite opposition from broadcasters, manufacturers and retailers.