Android SDK is the software development kit for developers who want to build applications for Android platform devices. The kit contains all the tools that a developer would require to create, test and debug their Android apps.Android SDK is open-source, easy to install and use, and is compatible with all operating systems (Linux, Windows, and Mac OS).
It is an open-source platform.
There is no licensing because it is open source.
I am using the free version of Android SDK.