How do I legally use brand logos on my app?

Usually, the agreement by which you are using the API will include trademark-related intellectual property provisions which outline how you many use the provider's marks (logos, placements, etc) in your service, if at all. If there are no such considerations memorialized in the agreement(s) by which you are using these APIs, and you want to use those brands' marks, it would be advisable to raise the issue with the brands during your API integration activities and obtain the proper license prior launch.

In general, when you use the trademarks of other companies in rendering your own services, you must get the permission of the owner whose trademark you are using, usually in the form of a license agreement. If you are using and displaying the API of another software program or website, the source code used in the app could be protected by a copyright and you may have to get permission to reproduce and distribute the API through your app.

I understand that your app will compile orders placed on certain websites and display them to a user of your app. The logos appearing in the app are taken from the various online shopping providers and may also display the logos associated with products that are in a users' shopping cart.

If you are simply using the trademark of a company to link to content on that company's website, the trademark use may qualify as a fair use because you are using the logo to refer to the company's own products. This is called a nominative use of the trademark.

On the copyright side, some websites provide a SDK that provides access to the API for different apps. These SDK's may be distributed under a particular license that allows use of the software, but only if the user agrees to certain license terms. You should review these agreements for each of the larger brands' websites to see if there are any restrictions on using the API. Also, there are terms of use that govern a users' interaction with a website; these terms may prohibit the use of certain third-party apps to access services provided through the website. You should review these terms of use to ensure that a user using your app does not violate the terms of service.

Prior to releasing the app, you should speak with intellectual property counsel so that they can evaluate your business and help you determine what licenses you might need.