Unity 5.x Editor freezes entire OS X system when project is opened (5.3.4f1, 5.4.0.b13)

Unity 5.3.4f1 and 5.4.0.b13 consistently freezes entire system (El Capitan 10.11.4) when opening existing project, or creating a new one. Project selection window appears and functions fine, but when clicking an existing project to open it, or creating a new project, the main editor UI starts to appear, but the system beachballs and freezes completely before the whole editor is drawn.

Typically, most of the editor UI will appear except for the Scene or Game tabs, where a black area appears in their place.

Have no ability to Force-Quit, Command-Tab, etc...whole system appears dead. Can ssh into the system from a remote, but can't do much except reboot.

Looking at the editor log (attached) shows the Main scene being loaded, the Shader Compiler being launched, then...nothing. No crash, just a completely frozen system with a beachball for a mouse cursor.

(Unity 5.3.3 does not seem to exhibit this issue nearly as much)

Excerpt from Editor.log:

Looking at the system Console messages, see the following logged when the initial project selector window appears. Do not see anything else being logged when a project is created or opened, as the system completely freezes at that point.

Unity messages logged to the system Console:

 

If you have mac plugged to an external thunderbolt display try to unplug it and start Unity again.

 

How I wish...unfortunately, it's just a basic iMac from a few years ago, using the main/built-in display.

Opened a bug:
https://fogbugz.unity3d.com/default.asp?787240_knalcuj1t32ksrj0

 

I'm not getting the issues you are, must be specific to your Mac model setup
My details: MacBook Pro (Retina, 15-inch, Early 2013)(El Capitan 10.11.4)

 

Same happens to me with basically every version i testet on my current MacBook Pro (Retina, 13-inch, Early 2015, macOS Sierra Version 10.12.6). I tested from Unity version 5.6.3.f1 up to the newest one 2017.1.1f1.
What i did to reproduce it:
- installed Unity
- entered my license key for the professional version on the first startup
- waiting or doing something in unity or in any other application
=> the whole OS freezed after round about 1 minute so i had to do a hard shut down and restart the machine

What i did to fix it:
- removed Unity
- installed Unity again
- start unity but did NOT entered the license key!!
=> using the personal edition was fine, no crash/freeze
- going to 'Manage License' => 'Activate New License'
- entered the license key to get the professional version
=> everything is working as expected.

I tested this multiple times with the same result. If you are lazy and want to save time by just removing the license and enter it again, it will freeze again. You have to uninstall Unity and do a brand new install.

I know that this post is quite old already, but may be someone faces the same or similar problem.
Hope that helps!