You can earn STUT tokens by doing activities in any course, free or paid. And these STUT tokens can be traded up to 50% to fiat money.
The number of STUT tokens earned in a free course depends on the duration on the course, and follows a 1/10 ratio in relation with a paid course of the same subcategory and duration. So you can earn money, but at a slower rate than by doing paid courses.
The goal of rewarding students with STUT tokens is to let them show their dedication and knowledge, mostly to enter the job market, and free courses are usually introductional courses.