Apart from trying to boost DX for esolangs, the idea is for this to grow into a platform where people can discover and play around with a variety of esolangs without leaving the browser. That's quite far away though - the project is quite early in development and currently only has 5 languages (Befunge-93, Brainf*ck, Chef, Deadfish and Shakespeare). Some features like non-debugging execution mode (0ms interval) are missing too.
Currently the entire source code[0] (core + language providers) is written in TypeScript and React. Esolang code execution happens in a web worker. I'm planning to add support for WASM-based language providers for better performance, particularly for non-debugging execution. There's also a wiki[1] containing a description of the core design and a guide for implementing and contributing new language providers.
Looking to hear some feedback on the idea and current implementation - bug reports are welcome too!