Mostly it doesn't matter. If you gave me a compete copy of our competitors source code and there was no restriction on using it I wouldn't spend more than a few hours looking at it. We already have our working code built on our architecture. It is quicker to recreate their algorithms from scratch in our project than to read their code. We might look into their code for something specific (probably their data file format), but even then it is likely we would document what they do and reimplement it in our system from documentation.

The above isn't just speculation. In a previous job I made third party scan tools for cars. One manufacture didn't provide their legally mandated documentation. When lawyers contacted them about it they panicked and shipped us their source code and the above is what we did. (giving us source code doesn't meet the legal requirements, but at least it was enough that we could get our features working)