As they are used, dlls ARE windows only. The PE file format is NOT natively supported on any other operating system except windows.
1) a DLL is exactly
the same as a Windows executable (but just exposes some "entrypoints" to other program)
If you can't run a (simple) windows-executable on a system than you can forget about (extra) DLLs too.
2) A DLL quite often uses other DLLs to work. Mostly those other DLLs are Kernel32, User23, etc (the standard Windows DLLs). If you do not have them (one way or another) on the target-system/OS you can, again, forget about using Windows-style DLLs on that system.
3) GM (and the executables it creates) allso depends on the availability of, for instance, DirectX. Although Direct-X exposes some
functionality by way of DLLs most of it is done by COM-objects (which are registered in windows, etc). Does your target device support them too ?
In short : The target-system would need to emulate quite a lot of what Windows does/is to be able to run GM. If it does not do that you can forget about "just" (re)writing a single DLL in the hope game will run.