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PlayCanvas is MIT-licensed. https://github.com/playcanvas/engine

Only the engine is open source, the editor used to create the apps/games is not. https://github.com/playcanvas/engine#playcanvas-editor

It's a bit more complicated than than. The front-end framework that the PlayCanvas Editor is built on (PCUI) is also open source: https://github.com/playcanvas/pcui Other open source tools like the glTF viewer are also built on it: https://github.com/playcanvas/playcanvas-viewer The rest of the Editor code is unminified and unobfuscated. The is done deliberately so devs can write extensions, report bugs and generally understand how it works. More of the Editor codebase will be open sourced over time.

Godot engine can export foe Web and has also been ported to run in a Web browser, although the desktop editor is probably more performant/reliable:

https://godotengine.org/

https://editor.godotengine.org/releases/latest/

To some extent https://www.babylonjs.com/