F4LL0UT: If it was present in the floppy version GOG's release has iMuse because that's the version GOG provides (alongside the Windows ports). I haven't really checked this version out yet but others have stated that iMuse is in fact present in GOG's DOS version.
Waltorious: My understanding is the following: GOG DOS version (original floppy version) has iMuse, but does not have much voiced dialogue. Also, the resolution is limited to 320x200. GOG Windows version DOES NOT have iMuse, but uses the X-Wing vs. TIE Fighter engine, which means 640x480 graphics with textures maps, and it includes fully voiced dialogue.
What most people want, however, is the one version that GOG does not have, which is the 1995 DOS CD-ROM version. This version has iMuse, fully voiced dialogue, and 640x480 resolution (but no texture maps). There were some hints that GOG is working on getting this version, but we have no idea how long that will take or if it will end up happening at all.
Yep, that's the version I would LOVE to have.