Of course. or you pay to have a server. and you will continue paying to solve future problems and add more content. or you learn on your own and you are not depending on anyone in exchange for money.
In my case I have decided to learn what is more beautiful.
It is true. I am learning java oriented to l2j emulators.
I found a book (manual) that the author is a developer of l2j.
If anyone is interested, I send it