For most courses, the answer is 'Yes.'. If you weren't sent to OLI by a teacher or your employer, and you just want to learn on your own, you're an Independent Learner. These are the types of courses available to you:

Independent Paid courses:

A few self-paced OLI courses are available for a modest fee. They include auto-graded assessments and some (but not all) offer a certificate of completion.

Open & Free courses: 

Many of OLI's courses are available for free, without any of the graded assessments. There are no teachers, no schedules, no certificates of completion, and no credit. They are simply free learning materials.

OLI's Independent Learner courses