I have the same problem as Thoth since the update released yesterday night or this morning. I am also on Mac OS Mojave 10.14.6.
It has me quite anxious as I have a monthly game I'm supposed to be running this evening with people traveling a fair distance to play and all of my encounters are built in my Hero Lab install.
I mindlessly installed the latest version on top of my old version when I saw there was an update and now it crashes on start.
Is anyone aware of an archive of past versions of Hero Lab so I could re-install the previous version?
Here's my crash log:
https://pastebin.com/UcixRF3q