Minecraft Modern (officially Minecraft: Java Edition) is one of the two updated versions of Minecraft which require a paid account to download, update and play. Most of the new development projects focus on either creating entirely new programs from scratch that interoperate with Minecraft (such as a bot or server) or modding projects that wrap the client or server and provide bug fixes, new features and enhancements to existing features.
Documentation
There are ongoing efforts to keep reverse engineered documentation updated, but it isn't as easy as it sounds. The protocol generally changes slightly with each release, and both the Client and Server classes get rearranged on each release. Below are links to the current documentation segments, which may or may not be completely up to date.
Minecraft: Bedrock Edition is the multi-platform version of Minecraft.
It is available for mobile, Xbox One, Nintendo Switch, and various other platforms.
Pocket Minecraft (or Minecraft: Pocket Edition) was the prior version of Minecraft for mobile devices.
It was replaced by Minecraft Bedrock on November 18, 2016.
Documentation
The protocol and map format documentation for Minecraft: Pocket Edition.
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 2009, and because it is very simple, there are many programs made to work with Classic.
Documentation
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 provide insight into how specific features work or can be accomplished, and by themselves are generally free to use in your own program.
