Originally a commercial product, Executor was released as freeware and open-sourced by the authors in I have tried several versions of this programme, and they are all capable of running Mac Warcraft. But recently I learned about an emulator or rather, a compatibility layer called Executor which does not have these requirements. There exist a number of free, open source Macintosh emulators a good overview can be found at this site, however nearly all of them require a ROM image obtained from an actual Mac and a copy of MacOS to run. And even though a Mac demo was released by Blizzard, running it without a Mac is not possible. However, apparently it is almost impossible to find any good quality screenshots of the Mac version on the net these days.
This is why some Mac ports of PC or console titles received updated graphics to match the increased resolution compared to the originals.