By default, the DIscourse software that powers this site uses Gravatar as a source for user pictures (getting the one linked to your email address as provided in the Fedora Account System. Gravatar is provided by open-source company Wordpress, but isn’t open source.
I think we should change to this for Fedora Discussion and Ask Fedora, but it will cause anyone who hasn’t set an avatar here locally to get a new one, which may be surprising. Additionally, new users without a open source / free software background are much less likely to have an avatar set up with Libravatar, so we might want to do something different on each site.
Yes, I think that is the case. I’m actually not 100% sure what will happen with existing users. It may be that they keep the current avatars, which would be fine.