Apple has dropped support for 32-bit binaries in the latest release of MacOS X, 10.15 (Catalina). This change impacts VMD because VMD depends on two externally developed cross-platform graphical user interface, FLTK, and Tk (from Tcl/Tk).

While VMD has supported 64-bit platforms for 20 years, the "catch" in support for 64-bit MacOS X is that 64-bit MacOS X requires different graphical user interface APIs in 64-bit mode than it does in 32-bit mode, resulting in some ongoing stability problems for the FLTK and Tk libraries that VMD depends on.

The issue is that we have to create a specially modified version of FLTK (which is not written by us) to be compatible with both Catalina and Tcl/Tk. As yet we don't have any ETA to provide users at this time.

We are working on building a version of VMD for MacOS X Catalina, using patched versions of FLTK/Tk that resolve their MacOS X-specific 64-bit incompatibilities, but as yet this work is still ongoing. When we have something that is ready for testing, we will announce here on the VMD web site and on the VMD-L mailing list.

Apple deprecation of OpenGL, OpenCL support: In the long term, we have serious concerns about ongoing support for MacOS X, since Apple has officially deprecated their support for OpenGL, the graphics API used by VMD and thousands of other scientific visualization tools. Further, Apple has also deprecated OpenCL and CUDA, and MacOS X has no planned support for cross-platform rasterization or ray tracing APIs such as Vulkan. All of these developments give reason for concern about the long-term viability of MacOS X as a platform for scientific visualization applications.