Software licensing of free abandonware

Question

I recently found the game that was my first encounter with a computer, a DOS game running in text mode. It was released in 1984 and is available on abandonware sites, but I've started to wonder if I may make a modern version of it (hopefully being able to release it as open source).

In the game, there's a copyright notice, and a message that it's a "free copy" which may be copied and given away. All I've got is the binary file, i.e. no source code.

1. Am I allowed to disassemble the program to study it?
2. Does the copyright apply to the code (implementation), the behavior, or both?
3. Does a clone need to be different or can I make a virtually exact duplicate as long as I write my own code?
4. Assuming that I'm allowed to create a clone: Can't, may or must I include the original copyright owners in the new copyright notice?
5. Finally, may I publish the code under a permissive license, or would that be a bad idea given that the original game was closed source?

Answer 1

Looks like you're not the only one who's ever had this problem. This may be helpful:

... You can copy all of gameplay without any issues at all. That is not copyrightable or enforceable. The things that matter are assets - art, sound, music, video, etc. For example if you take ZX game and clone it with your own assets you will be perfectly fine doing that. But if you take some asset and use it in different kind of game all together, it could be enforceable. There are loads of examples of this in the industry, for example first Warcraft basically copied Dune 2 gameplay mechanics and the genre was totally new at the time. For a more recent example - check out Gameloft company, the developer for iphone. What they do is copy successful game ideas as close as possible to the original but without using any art assets from originals. That is their successful business model. They copied games like Halo, Starcraft, World of warcraft and so on with huge success in their field. It is even funny that if you check their wow clone you may see that animations of orcs and their looks are very close to the original.

TL;DR version: As long as you copy gameplay and don't copy any assets (art, music, animation) you are 100% fine.

Answer 2

Note: This is more of a law question than a programming question. Consult a lawyer of your country if you need to be 100% certain.

On your questions:

1. Am I allowed to disassemble the program to study it?

   No. You are not allowed to disassemble or reverse engineer for that purpose.

2. Does the copyright apply to the code (implementation), the behavior, or both?

   The copyright only applies to the implementation. However, depending on the lawyers, judges and country, sometimes suing on the behavior can be successful. For example, Nintendo successfully sued the makers of The Great Giana Sisters over copying from Super Mario Brothers despite that (to my knowledge) no copyrightable assets were copied.

3. Does a clone need to be different or can I make a virtually exact duplicate as long as I write my own code?

   Exact duplicate will not be possible, if you create your own assets there will inevitably be differences.

4. Assuming that I'm allowed to create a clone: Can't, may or must I include the original copyright owners in the new copyright notice?

   Attribution is not required if your code does not violate the original copyright owners' copyrights.

5. Finally, may I publish the code under a permissive license, or would that be a bad idea given that the original game was closed source?

   Given that you do not violate the original copyright owners' copyrights, the new stuff is yours, and you can do with it what you like. It's yours, you decide on the license terms.

Note that some game mechanics, although they look like behavior, might be protected by copyright law. If they are very original ideas, or if the game mechanics are easily encoded as a lot of data, they could be copyrighted.

Disclaimer: I am not a lawyer, if you want to be sure, consult a lawyer.