I understand it is not always easy to fit other courses with this intensive course. On the schedule you will see that most lectures are in the morning and other activities in the afternoon. I am sure with some help from your fellow students, you can combine other courses with IN5010!
However, the 80% participation requirement in IN5010 is still applicable and can't be negotiated. All formal activities in the course fall under the 80% participation requirement. Optional activities have an (o) after their description and don't fall under this requirement.