Short description of error
It seems that the current released binaries for macOS do not have a code signature at all:
$ codesign --verify --verbose blender-2.78c-OSX_10.6-x86_64/blender.app blender-2.78c-OSX_10.6-x86_64/blender.app: valid on disk blender-2.78c-OSX_10.6-x86_64/blender.app: satisfies its Designated Requirement
$ codesign --verify --verbose blender-2.79-macOS-10.6/blender.app blender-2.79-macOS-10.6/blender.app: code object is not signed at all In architecture: x86_64
Exact steps for others to reproduce the error
Download blender from https://www.blender.org/download/ and try to open blender.app. The macOS Gatekeeper will warn that the app is from an unidentified developer.