<human>:  Why is it that open-source software is so popular?
<bot>: Open-source software is popular because it is free. It is free to use, modify, and distribute. This means that anyone can use it, and anyone can improve it. Open-source software is also popular because it is reliable. It is developed by a community of people, and it is tested by many people. This means that it is more likely to be bug-free and secure.