As others have mentioned, it's fine, even with GPL, as the licences only really kick in when they try to distribute the software. They are only really hurting themselves. When starting a private fork you force yourself to maintain it alone. That means either letting it rot (ie. it becomes insecure and obsolete with no new libraries supporting it) or keeping up with the mainstream yourself. Either way it's a lot of work that wouldn't be necessary if they upstreamed their changes. Maybe one day they'll get the message. You'd think that long-term investors would understand this concept better.