Using this service probably counts as a "third party app or service" under your Microsoft Services Agreement. As of 9/9/2017, I see nothing against us using this app, so long as we understand that Microsoft is not responsible for their content, and we agree that any service agreement to this third party does not supersede the official Microsoft Services Agreement. Keep in mind though, that they can change this notice at any time without telling anyone about it, and on any given day the use of this service might violate that agreement. I seriously doubt that will happen, though.
In short... You're probably good :)
Here's the link to the agreement, so that you can check for yourself. https://www.microsoft.com/en-us/servicesagreement