How do you avoid being forked into oblivion?

Licenses and trademarks allow you to maintain control over your software.

by Stack Exchange - Oct 25 2014
 
Den asks:
As recently reported, "Xamarin has forked Cocos2D-XNA, a 2D/3D game development framework, creating a cross-platform library that can be included in PCL projects."
However the founder of the project that was forked says:

The purpose of the MIT license is to unencumber your fair use. Not to encourage you to take software, rebrand it as your own, and then "take it in a new direction" as you say. While not illegal, it is unethical.

It seems that the GitHub page of the new project doesn't even indicate that it's a fork in a typical GitHub manner, opting for an easily-removable History section instead (see bottom).
So my questions are:

1. Was Xamarin's action and the way the action was done ethical or not?
2. Is it possible to avoid such a situation if you are a single developer or a small unfunded group of developers?

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