The reverse engineering of model formats was done by many people. See the application for full credits.
Contributions are very welcome! New games, new features, and bug fixes are all very appreciated. Even small contributions like proper map names, grouping maps and new default savestates are extremely helpful.
If you would like contribute, there is a Getting Started guide in the Official noclip.website Discord Server. A number of developers from the community are present there and can help answer questions if you run into any additional issues getting set up.