ScoreCam uses streaming services that do not require any fees to watch (YouTube Live, Twitch, etc.). The number of viewers that can watch depends on the service but, generally, there are no per-viewer limits.

As for privacy, you can make the stream Public, Private, or Unlisted, depending on your streaming service.

Here is more information for YouTube: YouTube: Change video privacy settings

Here is more information for Twitch: How to Private Stream on Twitch 

Services like Restream and Castr allow you to stream to multiple platforms simultaneously.