Non-commercial private version of Minecraft

I had a private Minecraft server that worked the same as the official server. People can sign up, choose aliases, change their skins, and use my game servers like they used the original version. I did this only for my friends and for myself, I have NEVER asked for any commission or made any profit. I did everything for Minecraft version 1.5.2. Now I tried to do this for version 1.8 and failed ...

I created a fully functioning launcher based on the original Mojang launcher, but when I tried to get the client to validate the credentials from my server, I ran into problems. I realized that I needed to have my own authlib.jar file, so I changed the launcher to redirect the connection through my server when the launcher loads the library files. It works and downloads a custom authlib.jar file from my server. I think the only thing I have to do is modify the authlib.jar file to validate the credentials from my server, but I cannot do that because I lack the necessary skills ...

ANY help is appreciated. I have been taking this service for over two years now, my friends were happy to use it (it was only for a few people, so it wasn't a big loss for the gaming community.) And I never advertised my server to anyone. Hope you guys can help me do this, if not this project seems to be coming to an end. This is my first post and I don't even know how to use this site well. The only thing I know is that you guys are much better at programming than me. And please don't mind my writing style, I know it sucks ...

Thanks in advance!