While there's no reason this is fundamentally impossible, there are several difficulties:

- Forge doesn't really have an API layer and expects devs to work directly against deobfuscated Minecraft code. Mods break every Minecraft version.

- Forge-level mods require cooperation from the client, beyond what the official client offers. Forge mods are structured so the same mod file runs on both clients and servers.

- Because of this, a server reimplementation providing Forge features must do one of three things: compromising on open-source by releasing a client mod, reimplementing the Minecraft client (hard, and hard to get people to use), or mods splitting in Forge-based client halves and new-API-based server halves (code duplication, hard to convince modders to not just use Forge).