A rather unpleasant thing happened not so long ago (3 days ago). Almost confirmed information that Blizzard closed opensource Diablo 3 emulator (Mooege).

For those who are not up to date, I’ll give a little insight into what kind of relationship OpenSource and some Blizzard projects have. Those who are in the know - can skip a paragraph.
WoW server emulators
As soon as Blizzard announced and launched its world-famous game World Of WarCraft (2004-2005), programmers with reverse engineering skills began to dig a protocol and create their own server that can be served by the official Blizzard WoW client and play the game mechanics in parallel.
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In general, this is called an emulator. In order not to pay money on the official server + it is possible to play on the local network, incl. with low ping.
Although, the goal was officially declared as an instructional one. They say that the players run here on a semi-working server, learn the basics, and go to the office. server. Well, including training for those who want to participate in the development of the project programming skills and not only. Well, okay, this is all the lyrics.
Emulators opened, closed, forked, etc., in general, live to this day. There were so many teams and projects that it wouldn’t have been possible to close them (and there’s a double question, some actually tried the game on pirates and went to the server). In general, Blizzy didn’t do anything with the open source projects of WoW emulators, but simply in their last supplement (Cataclysm) they started randomly changing opcodes with each patch (which are released quite often, once a month or three). That completely broke the protocol and took extra time from the developers on its parsing and updating. To this day (and already more than a year has passed) there is no sane emulator in the public domain for WoW: Cataclysm. In general, then they got out. So what about Diablo?
Diablo III Emulator
As soon as the beta client appeared, it immediately leaked to the "right" people and the developers started writing an emulator (C #, sqlite, going under mono). He was
named Mooege . The beta emulator has already appeared in September-October 2011 and has been developing quite actively. As soon as Diablo was released, the community quickly implemented all the innovations (the protocol) and completed the game mechanics,
which is much smaller than in WoW, and the process would end fairly quickly. Apparently, this scared Blizzard, and while the project at an early stage (there was not a year), you need to close it. No official information, but
It is clear that for Blizzard in this case, Mooege would bring (would bring) losses. Post, rather, simply informational, than criticism in side Blizzard. Just the first such case from them, this could happen before.