[Solved] Can't find the source codes of Minecraft

Hi, Iv got question is it possible at all and if it is then how to do it ? What are steps of such procedure? P.S. Iv got my own ideas.. but... maybe its simple then I think...

Please post complete logs as described in the FAQ (https://forums.minecraftforge.net/topic/125488-rules-and-frequently-asked-questions-faq/), it will contain more information that may help figure out what your problem is.  

These are the Forge forums, you'd probably be better off asking in a fabric forum, if they have one.

I've just created a server for my friends and I to play on, running 1.21.4 with Fabric. I've given them an instance that includes all the client side mods they'll need, but I've just now come across a problem, built into the nature of MacOS, that a specific client side mod fixes. If possible I want to use this mod as a server side mod, so my friends wont have to go through the hassle of adding it themselves. The mod in question is MacOS Input Fixes. The latest version (1.21.3) does work on 1.21.4. If this can be turned into a server side mod, what would I need to do to change its functionality? What programs would I need to install and learn?

when i start my save i have this error message  [Server thread/WARN]:Could not find value 'formations:template_editor' in registry 'minecraft:item' for @RegistryEntryAcceptor! What can i do ??