I’d like to write a desktop GUI program using Qt (which is itself is licensed under GPL) that interfaces a REST API and I want to use a strong copyleft license, preferably GPLv3. (I use the GPLv3 for all of my personal projects and they commonly share re-usable parts.)
The API Terms of Usage include this:
You may not require anyone to make payments, take surveys, agree to subscriptions, rate your content, or create accounts in exchange for access to Scryfall data.
My program will download data from said API during run-time and display information obtained using it. It will not ship any data obtained from it as part of the source code and setup bundles (if any).
The GPL, like any OSI-approved free software license, explicitly allows re-selling the application and commercial use.
Personally, I do not and will not intend to ever sell this piece of software to anyone.
The program downloads and displays (parts of) the information obtained via API calls, thus it ”grants access to Scryfall data”.
Selling the program (if done by a third party) violates “You may not require anyone to make payments […] in exchange for access to Scryfall data.”, thus the program can never be sold by anyone. It it were sold, the seller were requiring a payment for granting access to the data provided by the API, therefore violating the ToS. But compliance with the API ToS then violates the GPLv3, which explicitly prevents further restriction, aside from the ones made by the license itself. Thus this clause in the ToS contradicts the GPLv3 (and possibly any other F/L OSS license).
Therefore it is not possible to write free/libre open source software interfacing said API.
Is my interpretation right or wrong? I.e. is it possible to write GPL-licensed software interfacing the non-profit API or not?