DOS BGI and Windows 3.1 are no longer supported since release 4.0.
MGui 4.0 is available in the following programming environments:
GNU C under DOS 32 bit (by DJ Delorie)
GNU C under Win32 (MinGW home page)
Visual IDE based on MinGW (by Bloodshed Software)
GNU C under Win32 (RSXNT home page)
GNU C under Linux X11 & svgalib/ GRX 
Borland C++ Win32
Microsoft Visual C++ 5.0 Win32
Watcom DOS/4GW GRX and Win32
LCC Win32

Moreover, it can be easily compiled in any Unix/X-Window environments as SUN Solaris, HP-UX, IBM AIX, etc...

In order to use MGui in the PC Hardware platform, a 386 (or higher) processor and a VGA video card are needed.

A minimum 256 color resolution is required to use MGui Designer, 800x600 (or higher) pixel resolution is preferreable.
The 32 bit DOS/4GW is available for the Watcom 11.0 compiler.
The DJGPP version requires DJGPP 2.0.3 and GRX 2.4.5 (or higher), also available on Simtel.NET

The Windows version is supported via one of the GNU compilers:
MinGW32, Dev-C++ or RSXNTDJ v1.6.
Other supported Windows compilers are:
Borland C++, Watcom 11.0, Visual C++ 4.0, LCC.

MGui under Linux is supported in Elf Binary format and requires Glibc 2. Old versions of Linux featuring a.out format and older version of libc are no longer supported. In order to use MGui under Linux you need the X11 environment (both run-time and development kit) or GRX 2.4.5.