The bulk of the data for RadioListings was obtained from feeds provided by the BBC as part of their experimental "Backstage" project, which ran from 2005 to 2011 and was intended to open much of the BBCs data to its users. Its slogan use our stuff to make your stuff gives a good flavour of what they wanted to achieve. These feeds were free to use and had no copyright restriction, other than that the phrase supported by backstage.bbc.co.uk needed to appear.
Using this I was able to expand the manually collected listings for the previous decade - the online schedules used to go back to 1997 but were removed, with the BBC citing a lack of space for them - and keep the database up to date.
Although Backstage ended in January 2011 the data feeds are still running, and an alternative in the Programmes/Developers has been created.
Other information is provided to me by those who listen to the programmes and those who make them, and I've assumed that these contributions are intended for publication.
My own work is mainly in the organisation and rationalisation of the data, for example adding series and episode numbers, or matching repeats to the original broadcast, and verifying archive data on messageboards and specialist sites. I do not claim any copyright over the content, but would appreciate the appropriate credit when used.