Currently the project is All Rights Reserved. Pick an appropriate license and get approval from previous committers. (Does something like CC-BY-NC exist for software?)

There NC part doesn't exist for software, AFAIK. Not with the "common" licenses, anyway. As for the BY part, all the "common" licenses have that.

Personally I would suggest MPL, or L(?)GPL for a stronger protection against commercialization. Not a full protection, but it's going to be hard to sell something that's already available for free.

Hi all. As someone who develops a project with similar goals, I'd recommend GPLv3 or AGPLv3. Non-commercial licenses would arguably forbid y'all from collecting donations via Patreon or even your ko-fi (though I'm not aware of this having ever been enforced). Permissive licenses like MIT, Apache (which is what pyffmpeg uses) and weak-copyleft licenses like MPL and LGPL are fine, but I've worked in industry long enough to have seen how much corporations abuse these licenses to build and sell entire stacks while contributing nothing back.

I would personally recommend AGPL for the simple reason that this package could naturally be extended to a software-as-a-service application (hosting the converter on a server so the user doesn't need to download or install anything), and if you're going copyleft, you really want to plug that loophole.

IANAL and datapacks are not quite the same as mods, but they might be close enough to make this quote from Modrinth still applicable:

Typically, when a copyleft license is wanted, the GPL-3.0 or AGPL-3.0 would be used. However, these licenses are incompatible if linking into Minecraft, due to an issue with the difference between proprietary and free software outlined by these licenses.

Which is why I suggested LGPL and similar rather than full GPL. I've seen attempts to make GPL work, but I think it's better to stick with a standard text license than to try to invent a new exception to the GPL.

Then again, this is a generator and not a plugin, so maybe a more appropriate exception to look at is the GCC exception....

Thanks for linking the Modrinth blog—I'm not a lawyer either, and if there are reasons I shouldn't be using strong copyleft in my mods and datapacks, I should fix that ASAP.

Anyways, this project is not modding or otherwise touching Minecraft code, and, as you point out with the GCC exception, if products created with copyleft software we're automatically copyleft, then anyone who has ever used a copyleft text editor would be in serious trouble.

Ultimately, it's y'all's choice!