I believe Java also fits that list. The [Java Language Specification](https://docs.oracle.com/javase/specs/jls/se12/html/index.htm...) via the [Java Virtual Machine Specification](https://docs.oracle.com/javase/specs/jvms/se12/html/index.ht...) is implemented on the open-source OpenJDK project and many other free distributions exist, including from Amazon, Azul, IBM, Alibaba and others [1].

[1] https://en.wikipedia.org/wiki/List_of_Java_virtual_machines#...