Project Canvas will be formally incorporated later this summer. Its seven partners also include the BBC, ITV, BT, Channel 4, Talk Talk and Arqiva. It is aiming to launch a consumer product next year.
Desmond, who is chairman of Northern & Shell, said: "Project Canvas is set to shape the future of broadcasting. 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 Five’s commitment to supporting Project Canvas following a review of our digital strategy."
Richard Halton, director of Project Canvas, said: "Channel Five has already made a major contribution to Project Canvas and we’re delighted to have them back on board. This is great recognition of how important Canvas is to the future of television."
Five announced it had pulled out of further investment in Project Canvas on 9 July pending a review of its digital activity, although it said it was still likely to provide content to the platform and was supportive of its objectives.
On 23 July, Northern & Shell bought Channel Five, formerly known as Five, for £103.5m from RTL Group. It has since announced a raft of departures, including chief executive Dawn Airey and managing director Mark White.