Dan Bunten, the designer of M.U.L.E., claimed it would have been impossible to port the game to the Apple II (CGW, 12/84, p.40), despite that it was ported to the Commodore 64, the NES, the MSX, NEC PC-88, Sharp X1 and the IBM PC. The game was developed on the 6502-based Apple 400/800 machines. The Apple II uses the same CPU but is slower, but the C64 runs at the same speed. All Apple IIs can be upgraded to 64KB.
Fortunately, there is not a lot of music in MULE. There is one main song and a couple of little themes. Even with the Apple II's extremely limited sound capabilities, music and animation can be done at the same time (Prince of Persia is an example). The IBM PC has very similar sound hardware and sounds OK.
The Apple II has just enough hi-res artifact colors for 4-player MULE. Blue, orange, green and purple over white and black backgrounds should work just fine. The IBM PC port supports only 4-color CGA and PCjr. graphics and uses artifact color to support four differently colored players.
Control is slightly tricky. The Apple II gameport can support two joysticks or four paddles (analog) with but only has an odd number of buttons (3) to share between them. Most joysticks used two buttons and hogged the socket/port. Two players could use a joystick and two players could use the keyboard, just like with the C64 and PC.
Even though the Apple II does not have sprite graphics, this shouldn't be much of a problem when the game only needs to keep track of four objects at any one time. The IBM PC doesn't have sprite support either and the port does not suffer from any slowdown.