I am not a lawyer so I cannot discuss the details of whether it is exactly the same product or not but there are a lot of similarities (especially considering he interned at the place) which will make any CEO think. I mean IP protection is critical for software companies and whether the CEO is right or wrong here, I think it is unfair to shit on the CEO just because he is being rude/mean.

If you intern at my company and then build a very similar product, I will be concerned.