I think the ticket system on SourceForge would be the best way to submit this:
Indeed, there isn't a lot of stuff that needs to be implemented to remove glib as a dependency, for a single platform/architecture. Doing this in a clean and portable fashion however, leads one back to glib. So the way I could see this working would be to have native support for certain key architectures which gets optionally selected at compile time which causes a platform specific header and C file to be built (the stuff in fluid_sys.[ch]) which supplies the needed macros and functions. In order to do things properly, threading APIs like pthreads or Windows related thread functions would need to be used (depending on the platform). Some of the atomic operations may require assembler (a lot of this can probably get lifted from glib), which ends up being compiler specific. It may simplify things to only have libfluidsynth get built in these cases and leave out the fluidsynth executable. That may cut down on some of the platform support that needs to be implemented.
I'm not really available at this time to assist with any of this, so hopefully some other developer will step up and help integrate such patches.
Best regards,
Element