I've just registered as I would like to use the basemaps for a web-based project where users would be able to share travel photos and gps tracks of their trips. I've read from the Terms and Conditions, that I'm ok to use the basemaps as long as my app is under 1 million views a month and I'm not asking any money for it. However, once I start asking money I should register for a paid developer account.
At the moment, I'm just beta testing, and my website is free, however I don't understand how can I actually use basemaps on a paid account once I'd like to go in production. I'd be using ESRI-Leaflet, but there is no api_key, etc. as part of the URL. Also, how can I find out my tile usage, if it's not connected to my account?