Glowstone is a completely open source Minecraft server that doesn’t rely on any of Mojang’s code – meaning you’re free to develop for your needs, and you’re free to change it however you want.
Good for educational purposes, e.g: setting up a Minecraft environement for a classroom, that you can completely control and personalize.

Based on a single JAR (java) executable, can run on any platform.
Simply download the jar in a directory of your PC/Server and follow the installation instructions
At the prompt, you can type an “help” command to get the list of available options. (here below from a linux box)

You must also configure your minecraft client for logging in the local server.

After the login, you can simple interact with users via the console