In my understanding, porting DosBOX to DOS would mean to compile a real DOS executable (with DJGPP or similar tool) without any "running Win32 code on DOS" hacks.
Not really. I mean that would be a way to do that, but not the way I would like to do that. Since HX is a valid DOS runtime, just like DOS4G or DOS32A, I think it is a valid concept to compile programs to it. I no more think of it as a "running Win32 code on DOS hack", I see this runtime as an intersection of Windows and DOS. By talking about "porting DOSBox to DOS" I don't mean leaving HX, but changing functionality into something meaningful on DOS, but meaningless on other systems such as the passthrough option for anything. It would not be ONLY for sound hardware emulation even though it could be used that way, but, for another program, you could use it for memory map emulation, and as a video card emulator for a third one etc. Or any combination of those. For the mouse, for example, I doubt that anyone would ever need a DOS to Windows API translation just for a DOS API emulation to get mouse for an application when it could be done by a simple passthrough to the real device driver, but a software video "mixer" is useful sometimes. Another useful thing is the multithreading which I use to listen to music while doing anything else through simultaneous CD-ROM emulation with a cuesheet. It's okay, and I'm not shure that it can be really compiled to DOS with DJGPP, while it can be if it is compiled for HX. Also no need to implement soundcard support for it, because it is given by the HX runtime.