"AECL never publicly released the source code, but several experts including [Nancy Leveson] did obtain access for the investigation. What they found was shocking. The software appeared to have been written by a programmer with little experience coding for real-time systems. There were few comments, and no proof that any timing analysis had been performed. According to AECL, a single programmer had written the software based upon the Therac-6 and 20 code. However, this programmer no longer worked for the company, and could not be found.'
https://hackaday.com/2015/10/26/killed-by-a-machine-the-ther...
"AECL never publicly released the source code, but several experts including [Nancy Leveson] did obtain access for the investigation. What they found was shocking. The software appeared to have been written by a programmer with little experience coding for real-time systems. There were few comments, and no proof that any timing analysis had been performed. According to AECL, a single programmer had written the software based upon the Therac-6 and 20 code. However, this programmer no longer worked for the company, and could not be found.'