I'm planing to use the Imgur API in my own application. According to their document(emphasis mine):
Commercial Usage
Your application is commercial if you're making any money with it (which includes in-app advertising), if you plan on making any money with it, or if it belongs to a commercial organization. To use Imgur's API commercially, ......
Free Usage
The Imgur API is free for non-commercial usage. Your application is probably free if you don't plan on making any money with it, or if it's open source.
The problem is that I do expect some money from it: there is a "donate" button on every page. However, I'm also willing to make my application open source.
So my question is: Should I pay for commercially using the Imgur API?