Many gamers have been waiting for Blizzard to announce a new Diablo game for many years, but despite the lack of official activity, the modding scene for the series is alive and well thanks it's very enthusiastic fanbase.
This has culimated with modder / "hacker" Galaxyhaxz this past week managing to reverse engineer the source code for the original Diablo. He did have a little help though, in the form of Sony of Japan's own QA department, who seem to have accidently allowed a symbolic file to be bundled within the code for the Japanese release of the game. This file included the functions, data, types and other information needed to easily reverse engineer of the code.
Sony of Japan has long been known for letting things slide in their QA department. Anything from prototypes to full source code leaks (Beatmania), and Diablo was no exception. A symbolic file was accidentally left on the Japanese port, which contained a layout of everything in the game. This includes functions, data, types, and more! A beta version of the port also leaked, which contained yet another one of these files.
Galaxyhaxz has, nevertheless, spent four months working on the project and has finally released the original, reverse engineered source code for the game, bugs and all, under the Devilution GitHub Project.
The reason all of this matters is because it opens up a whole new realm of possibility to the modding community. As with other source code releases, such as Doom, significant changes are possible to the game engine, meaning anything is possible. Updated graphics techniques, engine enhancements, totally new gameplay elements, or even building an entirely new game on the same engine.
The main reason this has been desired by the community though is the difficulty many modders have when trying to mod for the game. Bugs that were simply unknown, or limitations within the game engine can often produce undesirable results.
Although this all sounds great, and no doubt the intentions here are very much innocent, it remains to be seen weather Blizzard will react to this, given the practice of reverse engineering is, at best, a grey area legally. While under DMCA laws, reverse engineering does have some fair uses, such as documentation or interoperability, any works that take advantage of the source will actually be falling foul potentially of copyright law.
One would hope Blizzard would turn a blind eye to this, given the age of the game, and community backlash it would no doubt incur should they attempt to stop people using the code. In the mean time, there's a whole bunch of new source code for modders and developers to explore and have fun with, and no, this source code won't allow you to obtain the game for free, either - it is devoid of al assets and on it's own, even if compiled, will not actually run.