FOSS? All I see is paid and no source.

You are mistaken, the source is available and the editor is free to download.

The project is indeed FOSS - it's licensed under MIT according to their GitHub repository (https://github.com/PixiEditor/PixiEditor), though they offer a paid version with additional features.

The repository says it's LGPL, not MIT-licensed.

Relicensed[1] under LGPL3 in 2023.

[1] https://github.com/PixiEditor/PixiEditor/commit/5db10cb8502b...

Always refreshing to see a new project opt for copyleft!