In the mid-nineties a company named Avanti stole code from Cadence Design Systems (where I worked at the time, though I had no involvement in the case). This was first discovered by an engineer noticing that error messages in the two systems were similar in ways that made no intuitive sense. Case was unusual in that several Avanti executives actually wound up going to jail for the theft.

https://en.wikipedia.org/wiki/Cadence_Design_Systems,_Inc._v...