A viral license is a type of legal agreement that companies use to protect the way their software is used. It's called "viral" because it is similar to a virus - it spreads from one person to the next, like a virus spreading through a population. With a viral license, your software controls how it is used and how it can be shared. The license will usually say that anyone who uses the software must follow certain rules, such as only sharing it with permission from the company, or only using it for personal use. This way, the company can make sure that the software is not being used for bad purposes.