The recent 6.0.1 / CC 2015.0.1 patch, released on April 30th is now available for manual download. One of the issues addressed by the patch is a crash on launch. Users not affected by this crash, or users on Adobe Creative Cloud, had no problem accessing the patch through the in-app or Creative Cloud update systems.
Users on the perpetual Lightroom 6 license, and who were experiencing the crash on startup, could not get access to the patch. Now you can download it manually.
You’ll need to scroll to the section titled “What if the computer that Lightroom is on is not connected to the internet?”