In the case of a document template with the data group Program Participant, you can call the name of the lecturer(s) using the mergefield below;
[OpleidingsDocent][DocentPersoon:NaamVolledig][/OpleidingsDocent]
The full name will be displayed, if you only want a first name or last name you will have to use a different mergefield.
NOTE: this mergefield is only workable for courses with one teacher.