Yes, you can use a free version of Canvas with Knewton alta. You would use the same instructions on https://support.knewton.com/lms-integration-documentation-and-faqs to integrate Canvas and Knewton at the admin and instructor level.
The key thing is to make sure that your students register with their school address when they first create their Canvas account. They can enter their school email address in the Username field when they register. This is important to ensure they’re able to communicate with you and our 24/7 Client Services team when they need technical assistance.