If you look at the UND web site it looks like the program is for all historically under represented groups. It is called the Cultural Diversity Tuition Waiver. That includes Native Americans, Alaska Natives, African Americans and Asian Americans. It isn't automatic, they have to apply. In North Dakota Native Americans make up the largest portion of those groups, so they get most of the available waivers. Most Native Americans do not receive tuition waivers. There are also some scholarships that are aimed specifically at Native Americans. People used to claim that Native Americans went to school for free, that is not true in most cases, but I'm sure there are some that do just like there are students in other categories that end up going to school for free.
You can also find scholarships and waiver programs to reward many other groups including the families of service personnel that have died, people from certain towns or counties, people studying specific subjects, students with disabilities, National Merit Scholars, etc. You can find a lot of information on these sites, although I'm sure they are not complete, http://www.ndus.edu/students/paying-for-college/grants-scholarships/#NDCTES and http://und.edu/admissions/financial-aid/types-of-aid/undergrad-scholarships.cfm.