VPNKodi can't tell if these streaming services that don't have licenses are legal or not. If a streaming service is found to be illegal, we let our users know right away and put a report on our website.
At first glance, it looks like 6stream is sending out content that is protected by intellectual property rights without the proper permission.
In short, the end-user is the only one who is responsible for the content they access through streaming services like 6streams.