Gosu is a general-purpose Java virtual machine-based programming language released under the Apache License 2.0. This general-purpose programming language is used in some open-source software projects, including the web application framework Ronin and the build-tool Vark, as well as in Guidewire Software commercial products for the insurance industry. The language is rooted in concepts from Java, C#, and ECMAScript, but borrows some constructs from Ruby and dynamic languages.