It's similar to oresim, but it's not the same. Both use a default game mechanic. Seedray was also just added, so we plan to add many more features that other clients do not have.
How can I find out the seed of the world? On servers with protection, different seeds are used for the worlds. Normal, Nether and End. All with different seeds.
SeedcrackerX my 19MisterX98 is better at locating seeds with antixray plugins. It will almost always work unless the server runs purpur/yatopia or other seed modifying forks of paper. His version also has warped cracker for nether seed, so you could find all 3 dimensions using different methods. (overworld with dungeon cracker and end with end gateways)