I found this interesting server software called “Diorite” which is basically just another server software that is written from scratch. But this one is really interesting and I quite like this. The World Generation is really nice and the simple physics allow for cool things such as floating blocks. It’s no good for playing survival but it makes a great creative server. With the unique world generation and simple physics, it feels like Minecraft classic or Cubelands. They have their own test server where you can enjoy this. You can join it by connecting to diorite.org in Minecraft 1.9.
I’m not affiliated with Diorite in any way; I’m just sharing an interesting server (software).
Here are some pictures: