Hello to all the boys … SBoyka am, I am interested rpg games
I’ma fan of rpg games especially medieval …
I have a desire to be active in the community …
I wanted to know which programming language is useful for programming in easyrpg?
and also collaborate with the project …
and in the future … Which language to use such scripts?
Y tambien se hablar en español… mi ingles no es bueno… 
Hola SBoyka welcome to the community 
If you want to contribute with code, player and editor are written in C++, most player code is using the SDL library and editor the wxWidgets library (is a GUI library like QT). The first place to get info about how works is the documentation wiki, which explains more details.
Adding scripting capabilities is not planned yet and there is still not any draft or solid proposal about it. Some talks in easyrpg IRC chat channel said something about create copy-pasteable simple commands for current event commands, like: show message “text” or something similar.