You are not distributing the code so you don't have to publish it. How are your competitors going to have this? You do not distribute, you do not publish your own additional code. You can use GPLed code as much as you want. If you want to distribute such software then you have to provide the code to your customers.You said this is not the case.

They are true masters of ... something.
They managed to have you as a user

for a few days

And this without a service whatsoever. best marketing ever. Only if they had a little something to keep you on that site after they managed to get you there.