Though this game being in Java, and modding also using the same Jar file, means it'll follow suit the same way as Minecraft Java modding in a sense. People can inject their own code into the game in some ways, and for dedicated servers, hosting their own 'modded' versions of the game and requiring players who have said 'modded' version to match.

You can mod almost anything down to the engine level. Hell, you could probably make your own games using this if you were dedicated enough. The modding system is kinda esoteric but also very flexible.