There's Progress In 2017 For Running macOS Binaries On Linux
Last year was a small update on Project Darling but for end-users it still left a lot to be desired with not yet supporting Mac GUI applications and a limited selection of binaries that could run under Darling. In 2017 that might change.
Project Darling Luboš Doležel shared that they are working to transition most of the files to Mach-O rather than sticking to ELF, which will provide a variety of benefits for this macOS translation layer for Linux. Darling is also working on a containerization approach with OverlayFS and there are two other developers who have joined this open-source project. There is also some experiments happening now for supporting GUI macOS apps on Linux.
Those interested in learning more about the current state of Project Darling can see this blog post update.