DOS - traditional 16-bit real mode DOS program with all well known troubles of DOS programs.
This version is the slowest, but there are no problems with rewriting code for 32-bit environment, and I think it's the most robust version.

XDOS16 - 16-bit protected mode DOS program.
This version lost any approaches after 32-bit releases were born and now is not supported (in source code I try to preserve compatibility with this version, so it can be generated at any time).

DOS32 - 32-bit DOS version. It requires any DPMI server that supports 32-bit mode. If you plan to use this program in "pure" DOS, you can download free redistributable CWSDPMI server. This version is the quickest. One minus - works only with short filenames. Same as 16-bit version run practicaly from any OS with DOS-box.
(Rem: CWSDPMI can be found at SIMTEL.)

OS/2 - 32-bit version for OS/2. As for performance, it is between DOS32 and WIN32 releases, supports long OS/2 filenames.

Win32 - 32-bit version for Windows95/98/NT. The slowest version. As for screen refresh speed, it works like any other WIN32 application (you can't go faster than Windows).

Linux - 32-bit version for Linux/i386. It supports both linux console (with direct raw video & keyboard) and vt100 compatible terminal.

Other native UNIX ports are in progress.