Yes, there are open source implementations of Java. Sun’s Java implementation (the most popular one), is one of them.

Why is Java open platform?

Java is open source because it has a version in which you could download its compiler source code. Detail: First, let us be clear about what is open-source. When we say an application is open source, it means that the distributor has a source code of the application for public access.

What open source means?

Open source is a term that originally referred to open source software (OSS). Open source software is code that is designed to be publicly accessible—anyone can see, modify, and distribute the code as they see fit. … Open source has become a movement and a way of working that reaches beyond software production.