Also interesting is that the Bing API TOS [0] has the below line that prevents users from using any other display advertising not provided by Microsoft:

"Display advertising that is not provided by Microsoft on any page that displays any part of a response."

DDG is big enough that they are probably on a completely separate agreement than the standard TOS though.

[0] https://docs.microsoft.com/en-us/azure/cognitive-services/bi...