To be honest I am surprised there isn't an open source alternative for this type of animation in 2D - I only know of blender and lottie as somewhat closer to it but nothing that is quite like Spine.
2D skeletal animation is an order of magnitude easier than 3d, but still a huge task in and of itself, with unique issues working with sprites compared to meshes. So it still requires very skilled understanding of art and physics, but there's a lot less demand as the AA/AAA industry is 99% 3d in the west.
It's not open source, but the best competitor to Spine is probably Live2D, which is used by a lot of Eastern studios (and basically dominant in the mobile space). You'd probably find some open source implementations over in Japan.
Spine is extremely polished, thought out and well written piece of software.
Expecting that somebody will do this kind of highest quality work for free is ludicrous.
We actually come from a strong FOSS background (Kryo, libGDX, and more).
For Spine, FOSS didn't make sense to us, as you either end up with open-core, which over time will shift incentives to work on the proprietary parts, or a donation based funding model, which is stressful and unpredictable.
I would not say same for Blender. Blender had absolutely god horrid UX for decades (it still has in many places) it is only very recently that they have gotten a bit better and polished some of the rough edges.
I don't know about Krita, but most open source software of considerable complexity and scope has god awful UX. It's no accident you named only two, of which Blender was infamous for it's bad UI and unintuitive nature.
Gimp is also the type of UX you generally get from foss.
> Blender had absolutely god horrid UX for decades
Yes, but it doesn't have it anymore: i personally know several 3D artists who switched from other (commercial, proprietary) programs to Blender and absolutely love it. You'll also find a ton of videos on YouTube from 3D artists praising it.
How it used to be is irrelevant because my point is that being opensource didn't prevent it to become a tool that is loved by its users for its UI.
It is also why...
> It's no accident you named only two
...i named Blender and Krita specifically (and intentionally, thus indeed not an accident) and did not brought up GIMP or anything else, because Krita is also loved for its UI (even if i personally am not a big fan of it, there are many artists who use it and like it).
My point was, again, that being opensource doesn't prevent having good UX - lacking good UX is not a byproduct of being opensource, it is a byproduct of the developers who wrote the software not caring about good UX.
Blender (via https://github.com/ndee85/coa_tools) and Godot's Skeleton2D node are both open-source. I'd assume Spine's advanced features far outpace them, but I also suspect the need for such features is rare.
