What kind of license is there for free templates for workflows? Can I build a website around such a free template and sell the service?

You can find n8n’s license here and an explanation of it here .

You can read my reply here that goes in a little deeper.

But you can’t create automations on your own n8n instance for clients, but you can create automations on clients own n8n instance. You are not allowed to host a clients n8n