With the generous free tier available (at least for the flash model), an app could potentially ask users for their API key, explaining how to obtain one if necessary, and then use that key for the user’s requests. Is this kind of usage allowed under the TOS? Is this an intended use of the free tier?
This is obviously not legal advice. The TOS states (in the section where services are free) “You may use API Clients for production use but Google may enforce rate limits.” There follows a list of reasonable prohibitions (like don’t put stuff that is beta into production). Assuming you don’t run afoul of any of those prohibitions, it looks as if that use is allowed under the TOS.
I do see a potential adoption problem, however. I mean a problem with attracting end users, not with Google. Ok, I am a customer and this app I just downloaded from the App Store is asking me to get an API Key. I go get the API key and the place that makes it for me says “be very careful with your API key and don’t give it to anyone else”.
Do you see where I am headed with this? Will even 10% just ignore the warning they just got and plug in their fresh API key into the app? A process step where 90% of potential customers will back out is probably not going to work.
Anyway, my thinking might be too conservative and I could be wrong. An experiment would help figure out what the actual loss in conversion rate would be.