The short story is: Mojang expects you to have updated your computer and operating system, there will be no fix. It seems like it would be trivial as the launcher and other versions work fine however they don’t want to spend any time on an old operating system and hardware. I will add the link to the mojang help site when I find it.
Mojang is pretty good about this stuff but I am always annoyed when a working system is broken by the developers. I understand the need to update the launcher because of heartbleed, but they didn’t need to break my working game. As I have a 1.5.2 server set up on an old mac, I need to be able to run the 1.5.2 client on the mac mini. Telling me to buy a new computer is not a solution. Now I can’t play with my son on our own server as we have only one computer that can run the older version (1.5.2) which to my mind is bizarre; that the newer system can play the older version but the older system that could play it before now cannot. At any rate it appears it will not be fixed unless some other software update fixes it tangentially somehow.