Isn't this kind of the point of free software? To provide software that is equivalent (or better than) proprietary alternatives, and allow users the freedom to run, copy, distribute, study, change and improve the software?<p>Are gnu coreutils "unethical" because they reproduce the proprietary unix command line tools with a free software equivalent? Is Linus responsible for informing everyone how Linux was originally inspired from Minix?<p>If I want to study how Threes was implemented, I can't. I can't modify the source code to implement new mechanics, I can't port it to new platforms. The only platforms Threes supports is iOS and Android. I don't have any devices with either OS, so I would not even be able to play the game. On the other hand, the free software 2048 has been ported to work in many more environments, such as the Web and even the Atari 2600! Threes would have never done that, not in a 1000 years.<p>Also just look at the burst of creativity, and inventiveness 2048 spawned. Now there are tons of derivative projects, each created by someone to tweak the mechanics and provide a new spin on the idea, ranging from simple tweaks, to full blown AIs, and even more advanced projects. And the source code is available to all to study and learn from. Threes inspired none of that. If Threes' developers had had their way, 2048 would never have even existed. Everyone who was interested would have to play the game Threes exactly as it was, and would not be allowed to change it, to experiment, or to express their creativity. They want to lock the user down.<p>None of this would have been possible from Threes, but it is possible from 2048.<p>If no-one buys Threes anymore, and instead uses 2048, that is not 2048's fault. It is not the job of free software developers to promote and support proprietary software. Should LibreOffice be required to do marketing for Microsoft Office, and give all users a link where they can purchase it?<p>Requiring everyone to reference Threes in each derivative is ridiculous. There is a reason why no one uses the original 3-clause BSD license anymore.