Hi Kerrigan - good questions! The post said, "to contribute to your jam project in any way you like, either by joining your team or completing a single task", so it's not to help only.
This is just one of the assignments the class have been asked to do. They are also working on longer term projects in internal teams. The point of this one specifically is to get experience of collaborating and communicating with a new team and documenting the process at some point during the semester. (I'm the lecturer who set the assignment and I made the first post as a jumping-off point.)