For as long as SpaceEngine has been around, people have been eagerly inquiring about cross-platform support. Mac support in particular has been asked about a lot recently. SpaceEngine will indeed be ported to Mac, and Linux, in the future (though not soon, as a lot of work needs to be done before then), but I want to make an important note about an obstacle that will exist to running SpaceEngine on most Macs, even after it becomes fully compatible with the operating system. That obstacle is graphics hardware.
As most of you know, SpaceEngine is a graphically intensive program and has strict graphics hardware requirements. SpaceEngine is guaranteed to work ONLY on proper gaming-class graphics hardware; this means Nvidia GeForce cards and AMD Radeon cards.
At present, the ONLY computers sold by Apple which meet this requirement are the 27" iMacs. Smaller iMacs, Mac Minis, and MacBooks only have integrated Intel graphics, and Mac Pro and MacBook Pro have workstation-class graphics hardware. Past testing has shown that Intel graphics and workstation graphics usually do not run SpaceEngine very well.
So while SpaceEngine will be ported to Mac in the future, Mac users should keep their hardware specs* in mind when that happens.
*To check what graphics hardware your Mac contains, click on the Apple logo at the top-left of your screen, then click on "About this Mac" at the top of the list. If next to the word "Graphics" it doesn't say something like AMD Radeon R# ### (e.g. AMD Radeon R9 290M), then SpaceEngine might not run properly on your computer when it becomes available for Mac.