amber
A Crystal web framework that makes building applications fast
...Amber is licensed under the MIT license, which makes it perfect for use in commercial applications. Instead of having to plan where things go, Amber comes with a set of conventions to guide you in developing your application. Tools are built-in to prevent and mitigate common attacks against web applications. Minimize the risk of SQL injection, form tampering, cross-site request forgery, and several other attacks. Crystal is a type safe, compiled language inspired by the simplicity of Ruby.