Qlik Sense Proxy Service API, Qlik Sense Repository Service API and Qlik Sense User Directory Connector API are REST API and can be consumed from all languages and environments that supports REST.
Qlik Sense QVX SDK and Qlik Sense .Net SDK are .Net libraries that can be consumed from all languages and environments that supports .Net such as the Windows plattform.
The Qlik Sense Backend, Extension and Mashup API are javascript libraries.
The Qlik Sense Engine API is a web socket API that can be consumed by all languages and environments that supports web socket.