[pricechild]

I don't think this is true.

The GPL allows you to copy & modify code for your own desires very generously.

The limitations you fear apply if you distribute the code (in source or other forms) or modifications yourself.

[jeroenhd]

That's true; assuming you run the software on your own premises, GPL won't hurt you at all. If you sell premium software packages to be run over at your clients' hardware this can be a problem, though.

However, after looking into Keycloak more closely, the software seems to be licensed with the Apache 2 license, so none of this is a concern.