There is nothing that prevents Wikiversity participants from leading and attending "courses" within Wikiversity. Wikiversity participants will do what they think is best for the project, and for many people education implies "courses". However, conventional courses typically imply certified teachers at accredited institutions in classes that exist for a specified duration and including a fixed group of students who are graded and earning credits towards a degree. Wikiversity does not have conventional courses. At best, Wikiversity can have non-conventional "wiki-courses".
What is a course? 
Outside the Wikiversity context 
- Hierarchical meaning: a course can denote a learning object with a large level of granularity. That means it is relatively large and consists of many learning objects with smaller granularity. Depending on the nomenclature being used, smaller units at the next level might be "lessons", "modules" or "sessions", but other terms could also be used. In some educational institutions, "modules" have larger granularity than "courses" - i.e. one module may contain more than one course. A course in this sense is typically delivered over a period of time, with its constituent units being delivered at particular points during that period.
- Evaluative meaning: the word "course" may also emphasize the evaluative side of education. Institutions of higher education may attach credit points, grades or other systems of evaluation to courses. However this is not always the case. Sometimes modules are the unit for evaluation, and sometimes stand-alone examinations which have no direct association with any particular course.
Inside the Wikiversity context 
Within Wikiversity, the word "course" only has a hierarchical meaning (see WV:policy proposal on structural nomenclature). The Wikimedia board has explicitly guided Wikiversity away from offering courses which include Wikiversity-offered evaluations coupled to earning credit towards a degree.
A possible exception might be when the evaluative component is in fact provided by an accredited educational institution which explicitly makes use of a specific Wikiversity course. Such an arrangement might allow students to use Wikiversity as a medium for providing course content for use by a credit-awarding institution. Note: this is hypothetical; however courses at real institutions do seem to have made use of Wikiversity as a space for sharing some of their work.
See also 
- w:Course (education) (in US usage)
Where are the courses? 
The wiki user interface is not well-suited for conventional courses and the Wikimedia Foundation Board of Trustees has directed the Wikiversity community away from courses (the Board's comments). Wikiversity participants are encouraged to innovate and create learning experiences that take full advantage of the wiki format for online community interactions. Non-traditional Learning Projects and other projects oriented towards learning about conventional course subjects are encouraged within Wikiversity. See: Wikiversity:Learning.
There is danger in using the word "course" in the names of Wikiversity pages. Visitors to Wikiversity are likely to assume that "course" means conventional course. It is better to not include "course" in Wikiversity page names. You can describe a Wikiversity learning project as a "non-conventional course" when you are describing the features of a "wiki course".