While don't know how their arrangement with Microsoft works, anyone can pay for API based access to Bing.
Prices are here:
https://azure.microsoft.com/en-us/pricing/details/cognitive-...
Prices are here:
https://azure.microsoft.com/en-us/pricing/details/cognitive-...
Little known fact: if you buy anything on Amazon, DuckDuckGo gets to know exactly (the precise item) you bought as part of the Amazon affiliate program.
This isn't specific to DuckDuckGo in any way whatsoever. This happens for ANY affiliate. I've used the Amazon affiliate program, and every month I would get reports of the exact items people were purchasing. I couldn't link those purchases to any particular individual, mind you, but I could see exact items.