Panelist in a Webinar

Hi, @fmonnet.  The simple answer to your question is, "No, a panelist in a Webinar does not need a Zoom license."

It's always best for attendees to have a Zoom account, but anyone attending a meeting scheduled by someone else only needs a Basic account, which is free.  You are correct in asking about a Zoom license... a panelist does not need a paid license to join a webinar -- only the host is really required to have an account with a paid Webinar license.

I hope that helps!