I don't know enough about guile, but janet was pretty easy to develop for .

Its binaries are quite small, could wrap and embed raylib and a few small c libraries with no hassle. This makes distribution much easier.

For my simple 2d game jaylib (raylib) code.

  ls -laoh build/app
  -rwxr-xr-x  1 worthless   2.8M 27 Jul 17:28 build/app

  otool -L ./build/app
  ./build/app:
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1356.0.0)
        /System/Library/Frameworks/Cocoa.framework/Versions/A/Cocoa (compatibility version 1.0.0, current version 24.0.0)
        /System/Library/Frameworks/CoreVideo.framework/Versions/A/CoreVideo (compatibility version 1.2.0, current version 706.41.0)
        /System/Library/Frameworks/IOKit.framework/Versions/A/IOKit (compatibility version 1.0.0, current version 275.0.0)
        /System/Library/Frameworks/OpenGL.framework/Versions/A/OpenGL (compatibility version 1.0.0, current version 1.0.0)
        /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit (compatibility version 45.0.0, current version 2674.3.0)
        /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (compatibility version 150.0.0, current version 4034.0.0)
        /System/Library/Frameworks/CoreGraphics.framework/Versions/A/CoreGraphics (compatibility version 64.0.0, current version 1951.0.4)
        /System/Library/Frameworks/CoreServices.framework/Versions/A/CoreServices (compatibility version 1.0.0, current version 1226.0.0)
        /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation (compatibility version 300.0.0, current version 4034.0.0)
        /usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0)

The LLM's really can't deal with janet though, they seem to think its clojure and screw up a lot of things.

Feed your LLMs the documentation and example code (perhaps the whole stdlib if it fits). Tell your LLM that it is not Clojure nor Scheme, it is a different language. I have worked with more niche languages than Janet with Claude before this way, successfully.