BBC regulators have said the corporation must develop its iPlayer TV download service for Apple Mac and Linux users, as well as those using the Windows platform.
The decision comes after the BBC said development of a TV download service for Mac and Linux users was not guaranteed and would depend on cost. But the corporation has promised video streaming for those platforms, as well as Windows users, by the end of 2007.
Ashley Highfield, the BBC's director of Future Media and Technology, said on Monday: "We need to get the streaming service up and then look long and hard at whether we build a download service for Mac and Linux."
However, a spokesman for the BBC Trust said it had approved the iPlayer on the condition of "platform neutrality".
The iPlayer allows viewers to download a selection of TV programmes from the last seven days to their PC, and watch them for up to 30 days afterwards.
The BBC claims more than 250,000 people are using the service regularly, and it hopes to have 500,000 users by next April.