If its just plugins, then you are limited to java.
You need to know basic maven, spring mvc and struts.
I had developed plugins long back.
I am not a java dude, but when I was developing plugins, i took the struts.xml 's as the base to start finding how jive code works and then added my own actions or modified some of the jive's actions.
Thanks for raising this inquiry into the development languages used by Jive. As Pawan has mentioned, we use Java. For any additional development specific questions, I would encourage posting your questions to the Jive Developers space as needed, as this is outside the general scope of Jive Customer Support.
Let me know if you have any other questions with this.
thanks for your answer jeph!
for my future questions about dev-related things, will post them in the Developer space.
thanks for informing!
All the best,