Prior to OSX 10.6, ATSFontActivateFromFileSpecification/ATSFontActivateFromFileReference were available and could be used to load a font from a file. I can\'t find anything
Here's an updated version of how to do this in 2020. Much simpler now. Used 12 as arbitrary type size.
let fontURL = URL(fileURLWithPath: "path/to/font.otf")
let fd = CTFontManagerCreateFontDescriptorsFromURL(fontURL as CFURL) as! [CTFontDescriptor]
let theCTFont = CTFontCreateWithFontDescriptor(fd[0], 12.0, nil)