An open source license formalizes what people are permitted to do with the material that is open source and under what conditions. For example, this might address whether you are granted the rights to use, modify, or distribute (commercially or non-commercially) the material.
When you author a creative work, such as code, you automatically hold exclusive copyright to the work by default. Unless you include a license that specifies otherwise,
nobody else is permitted to copy, distribute, or modify your work without opening themselves up to legal action by you. Once the work has other contributors (who then each become a copyright holder), “nobody” includes you.
If that is not a legal mess you want to get into, your code should include specific terms and conditions for what different people are allowed to do with it, in the form of a license.
Disclaimer: It is not the goal of this chapter to provide legal advice. The goal of this chapter is to provide a starting point to help you make an informed choice by providing information on popular open source licenses in a simplified fashion. If you have any questions regarding the best license for your code or any other legal issues relating to it, it’s your responsibility to do further research or consult with a professional.