Open-source, except for the "new framework used to make Loop's settings window", so don't expect to build from source.
But "open source to those who pay" is quite a stretch of the definition.
If you check Open Source Initiative's list of approved licenses, you won't find anything that fits this definition:
https://opensource.org/licenses
The closest I know to what you're describing is Business Source License (BSL):
https://en.wikipedia.org/wiki/Business_Source_License
> The Business Source License (SPDX id BUSL) is a software license which publishes source code but limits the right to use the software to certain classes of users. The BUSL is not an open-source license, but it is source-available license that also mandates an eventual transition to an open-source license. This characteristic has been described as a compromise between traditional proprietary licenses and open source.
Just call it what it is, there are no feel-good points for advertising it as something it isn't.
People are ambivalent about BSL licenses because of the way companies use them to step back from their previous commitment to open source.
They're still an improvement over closed-source licenses.
It's a bit of an honor system because is allowed to just publish it for anyone to download for free but it's absolutely something you can do.
Of course the copyright holder can license new distributions under a different license (or different licenses at the same time). But are you saying that a copyright holder post hoc can revoke the license?
Wouldn't that be kinda weird? Suppose I buy some proprietary software (without any dependencies) because it's GPLv3, and then when I wanna exercise my rights, the sole copyright holder just goes "nah, when I think about it, this is actually not GPLv3".
(If you are correct, I guess that situation then might just be a civil case unrelated to the actual license where I essentially didn't get what I paid for)
Of course, the terms in GPLv3 that puts limits on the licensee / user (like that derivate works must be GPLv3) are not relevant.
But section 6 in the license stating that the source code must be distributed still holds true. Either OP distributes the source code to people who have the binaries, or the work is not licensed under GPLv3?
How do you plan on monetising Loop?
Currently, the only way I am making money is via donations, and it seems to be working much better than how I initially was doing, so I'll see based on how these first few weeks with 1.0 ends up.