This has a new protocol compared to 2.1. It also features many numerous fixes and new features!
Linux has Debian 64-bit precompiled binaries, but you can compile your own as it also contains the source.
If you are using Mac or other operating systems, download the Linux package.
The server pack is ready for both Windows and Linux, but you might need to compile your own for linux (source included)
If you are using Windows and require the source code, download the source package!