Perhaps the reason no one has answered is that you need to sign up for a Thomson Reuters developer account before you can view any of the API information, and signups are closed to all except those who have been "invited". Hardly what I would consider "open source".

Anyway, it appears that they have an SDK and API that might implement multiple ways to get at their data, only one of which could be DDE. You'll have to use your "invitation" to investigate on your own.