Need help with signing key signatures (modpack

Hello I am currently scripting my own server but i am stuck on something, I have made an island life server with a custom mod pack the developer who done it has now left us and i am trying to pick up the pieces, i need to know if i resign the the custom keys to the name of the TCG keys will that allow people with the TCG pack to join, if this is not how can someone please tell me how

Thanks