PolyMc
What if you could put mods on a server, without needing it on the client?
Well, that's impossible. But we can try! Nothing is impossible!
Note: if you're a mod developer looking to make a mod that'll be solely used serverside, you might want to consider Polymer. It has some advantages and disadvantages over PolyMc.
How PolyMc works
PolyMc is unique in that it operates on packet level. This means PolyMc doesn't touch the mechanics of the mod at all. The server is genuinely modded. This results in the server being quite stable, all the hacks PolyMc does to display things are separated from what's actually happening.
PolyMc uses a host of techniques to automatically try and display your modded things. PolyMc also features a large api to customize how items/blocks/entities/whatevers are transformed.
Do you want to get started? Check out the wiki!
Building
Run ./gradlew runDatagen once. Then just run ./gradlew build