While it is strongly suggested to use open-source libraries and frameworks, often open-source libraries and frameworks are distributed under licenses that are specifically designed to prevent certain type of usage for example using them in closed-source software. It is important to understand how different types of open-source and free software licenses work, and how you can use them in your research projects at the center. It is important to note here that the licensing policy of the center is to release all software under the Apache 2 license. In Unit 5 we look at what a few of the different licenses are, and how they work.