Not sure if I'm missing something, but the submission title says "open-source" and in the tool's help menu there's a link to the repo (https://github.com/playcanvas/supersplat), the tool runs in your browser, there's no server involved besides a Web-Server hosting the files.

I found its repository after searching google. The license is MIT.

[1] https://github.com/playcanvas/supersplat

I remember a time when it was considered unpolite to ask a question without googling first. Is it still the case?