We're big supporters of making games (and just applications in general) that run on WASM platforms (web browsers mainly.) The Guile Hoot project is broken into several phases. For this first phase we're targeting the r7rs-small Scheme standard because it's rather minimal. In a future phase we will add support for as much of Guile as possible in a web context (no POSIX API, for example) and will figure out how to interact with the DOM to render web pages. Our goal is to ship applications built with Guile and Goblins so that anyone with a web browser can use them. The gamer in me is hoping we'll eventually be able to hook into WebGL/WebGPU someday. :)
And yes, Scheme implementations use a garbage collector. For Guile Hoot we are using the WASM GC extension. Native Guile also uses the boehm collector but it's going to be replaced in the coming years with a better one called Whippet. I should also note that Guile Hoot is not using emcsripten. It's using a purpose-built assembler, disassembler, and compiler that outputs WASM binaries.