Lisp Community

Hello! This is another Friday Social topic. Hoping that this will be more insightful than the previous ones and we will learn something useful from this.

What useful open source projects are written in Common Lisp? To keep it interesting, try and avoid posting links to your own projects because that could turn into a thread of self-promoters. Instead share open source projects developed by others that you have come across. Here goes the questions:

1. Name one project (that is not already mentioned by others in this thread) that is written in Common Lisp.

2. Which OSI-approved license is the project released under?

3. Are you the author of this project? (I recommend that the answer to this be "No").

4. Who is/are the author(s) or team(s) behind this project?

5. Why is this project useful?

6. What in your opinion is the best thing about this project?

7. If you could recommend only one improvement that should be made in this project, what would it be?

Restricting this topic to "Common Lisp" so that we do not end up with a large list of Emacs packages. We will do similar thread for other Lisps in future. The project must be open source.