Minecraft Classic is the original version of Minecraft, available for free to the public. It is still played by many people, with an active development community. As it's been around since 2010, and because it's so simplistic, there are many, many programs made to work with Classic - there are over 18+ servers alone, written in everything from C++ to PureBasic to Perl. It's highly recommend if you're planning to do a development project at this point to instead look into the Minecraft Modern specifications.
As there is no longer any work being done on classic, the documentation for it is stable. If you create something that works with it, it probably always will.
Source Code Snippets
Source code snippets provide insight into how specific features work or can be accomplished, and by themselves are generally free to use in your own program.
- Deserializing the level.dat file format (C, C#)
Tools and Mods
Useful information & links
- Clients - third-party Classic clients.
- Servers - third-party Classic servers.
- Libraries - libraries to interface with Minecraft data files or network protocols.
- Utilities - tools that interface with a client, server, or data files, such as proxies or bots.
- Wrappers - mods that override features in the client or server.
For more info, check out Minecraft Classic.