The project is worth an extra 4% of the grade, so you can do it instead of one of the homework assignments, or for the extra credit, or just for the fun. But projects tend to be difficult to complete in one semester (and only worth 4%), so you should take one on only if you are truly interested in the subject and have time for it. A project is not required and it will not count against your grade if you do not do it. You can work on it alone, or team up with another student for a joint project. The projects will be turned in electronically with turnin, but to Risto, not the TA.
It is also possible to do a project on something else than neuroevolution; it is up to you. However, talk to Risto about your ideas before you begin. Also, you don't have to wait until the project is assigned in the class to begin. The sooner you start, the further you'll get and the more fun you will have with it.