Apple has always been a part of Cyan’s history. Apple/Mac users are a very important part of the audience for our games. We’ve said it many times: Rand only uses a Mac at home and work.
However, those facts do not directly correlate to resources for Mac updates. Mac updates require substantial time and effort to continually maintain or rebuild the games from the ground up.
Changes and updates to Apple's hardware (example: migration from PowerPC to Intel), software (example: discontinuation of HyperCard), and the MacOS platform (example: switch to OS X) make the Mac a wonderful modern ecosystem, but can create sometimes overwhelming challenges to small developers trying to update older titles.
We teamed up with some really amazing people at Codeweavers who specialize in this sort of thing (and they're also Myst fans!). They’ve been able to make macOS versions of all the games from the Windows versions.
They are still working to update Myst IV, V, and Uru: Complete Chronicles for Mac players who are running MacOS Catalina or later. Thank you for your patience and continued support!