To answer your question in short, no, OSAP does not provide loans for part-time students.
If your course load is anywhere between 20 to 59%, OSAP considers you a part-time student and the application process for getting a student loan changes.
If you are not sure about the percentage of your course load, check with your school, and they will be able to tell you.
However, if you know you will be studying as a part-time student, there are other options open to you.
You can apply for a loan from Part-Time Canada Student Loan or for a bursary under the Ontario Special Bursary Program (OSBP).
Regardless of what you apply for, you have to first speak to the Financial Aid Office at your school. They, along with OSAP, are responsible for determining your eligibility.
Hope this helps!