The MMORPG in question has a Korean developer and a German publisher. It is pretty old, but is still live and running by the publisher. The game appears to be dying and has a very low active population in general. The EULA seems to prohibit packet-sniffing and reverse-engineering to "reproduce ... the games" by the wording used, however that does not seem to make it illegal. Merely voids ones contract between emulator-developer and the publisher, giving them the right to ban use of their servers/services, if I am not mistaken.

There was an excellent answer, in my opinion, on a related question in Law StackExchange [1].

I am a European citizen. It is meant to be a hobby project originally, but seeing as how much time it takes to execute, it is sad to not see the effort be financially profitable, especially considering the potential it may have. The intention is first to replicate, and finally to modify by changing experience point rates, quests, maps and more, to re-form the entire flow and experience of the player, differing from the original game.

There are leaked server files and possibly leaked source code to the server files, but I will not peek at neither the reverse-engineered leaked software, nor the leaked source code, as it defeats entirely the original purpose. Hence, unless I misunderstand, the "Chinese Wall" principle [1] applies, since packet-sniffing and reverse-engineering of the game client are the tools used.

Unless I have misinterpreted [1], the game client appears to be the major stopper, before even getting to the financial aspects.


If at all possible, how can one go from writing the MMORPG server emulator, from scratch, to running a profitable server, legally, for the specific game described above?

Also, an auxiliary question: is breach of the EULA illegal or immoral, in this case?


I want to explicitly point out that, as per [1], the server emulator would not be theft of code, but a recreation from the imagination. The work-flow to produce the emulator only involves dissecting of the game client and packet-sniffing of the communication between the original game server and the game client. The EULA does not state any legal action against these two methods. I have also added a secondary question to help out the discussion.

[1] https://law.stackexchange.com/a/48393/34023

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    You would be good to look into the history of bnetd, an opensource reimplementation of the Starcraft online server. Blizzard successfully sued its creators on several counts, resulting in it being shut down. en.wikipedia.org/wiki/Bnetd
    – user28517
    Commented Aug 18, 2020 at 23:28

3 Answers 3


Profit changes everything. There is a tradition of tolerance (mostly) for "fan projects" which are totally not-for-profit. However that goes out the window very quickly once profit enters the picture (if the original publisher is excluded that is; Black Mesa had a happy integration of publisher and fan profit, since they also run the game distribution platform Steam).

Because of the profit picture, licensing the game platform is your only viable option. And this is actually quite common; the original Half-Life (on which Black Mesa was built) had licensed the Quake engine.)

At the least you would be licensing the client-side engine. I suspect you also aim to license the client-side graphics as well; the publisher may have feelings about that since visual IP tends to dilute the uniqueness of their own game. For instance Half-Life did not reuse Quake monsters or art.

Art is a problem, because it also brings in lore

In a modern MMO, recreating graphics and art is a considerable task.

But if you don't, you may not be able to separate yourself from the conceptuals: If you were licensing a World of Warcraft client and using WoW art, it would be hard to justify purple, pink and green Elves without getting into the lore of the Night Elves and Blood Elves breaking away from the high-elf lineage... it would just be too jarring to use the same art assets yet have totally different lore... So at that point your game would become a "World of Warcraft story", which not surprisingly, the publisher would be much more reluctant to publish, since they want to retain creative control of their story, integrate it into their continuity, etc. Star Trek and Star Wars have whole staffs of "canon police" who make sure writers don't contradict existing lore, e.g. portray the Ferengi as a warrior race or Gungans in any way whatsoever.

If it's just the engine, that's easy

So if you are forced to change lore and art, and your plan is already to scratchbuild a new back-end... then really, all you're doing is licensing the game engine.

So now the question is, why would you rely on brand X's game engine, when there are plenty of other game engines whose owners are happy to license them cheap, and even ones that are open-source? For instance, a fan project is re-casting Half Life II into the Unreal engine.

So if we're not using that publisher's lore... and we're not using that publisher's art... and we're not using that publisher's engine... then we owe them nothing and we have a totally original game.

Look at a program like The Guild. It was based on World of Warcraft, but the team tweaked it a little bit so it didn't touch any of Blizzard's IP at all. They did that for a reason.


Since your question is about more than just replicating the server functionality, I will address the detail that is unrelated to producing a working copy of the server.

Even if you do manage to legally create a working server, if you don't license the right to operate, then such operation of the server would constitute a tortious interference in the licensing relationship that exists between the users of the game client and the original publishers/operators of the game. Whether or not this tortious interference would result in liabilities in the jurisdictions that you care about is a question for a lawyer who has your best interest in mind.

  • Thank you very much for your response, grovkin. Indeed, that is something that was covered in the post I am referencing in my question. I was hoping for a discussion on ways to legally get past that point, but by your answer it appears to be so that the only way to legally do this, is for one to get a license to operate, to avoid "tortious interference." Are you aware if the license for operation process would involve the original publishers/operators? If you could kindly edit your answer with any additional information. Commented Aug 18, 2020 at 10:14
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    @HelloWorld Such a license would typically be granted only by the studio or publisher. In fact, it's most likely that one of these might be the only one that can grant a license.
    – Trish
    Commented Aug 18, 2020 at 13:07

The only way to be entirely sure not to get into trouble is to get yourself a lawyer and ask them about the local laws in more detail.

In general, your EULA might bar you from dissecting or altering the program or trying to obtain the server code and it might remove your license to use the software if you do so, though enforceability of those provisions is a problem your lawyer needs to explain to you. You should ask them how to obtain a valid license to the server code, as it should be obvious you can't use code you have no license to or that you obtained illegally.

  • Thank you very much for this response, Trish. It appears my previous comment was deleted. Also, I want to clarify that I do not take this as legal advice, but only as a discussion which I would further continue with my lawyer, as you advice. One would indeed be dissecting the program, in this case, which would be a breach of the EULA. However, as the EULA does not state any legal action for the breach (dissecting the program), it only states banning access to the service. It is my understanding that this does not make the dissecting of the program illegal, is that correct? Commented Aug 18, 2020 at 10:07
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    The problem is, that it depends on how exactly the EULA is written. If it is written well, then your breach of the EULA prohibits any further use of the software. They don't need to specify any legal actions if further using the software is not allowed - which can alter your ability to decompile the software legally. Ask your Lawyer if you may dissect a software you may not use is legal.
    – Trish
    Commented Aug 18, 2020 at 13:10

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