SageMathCloud course subscriptions"We are college instructors of the calculus sequence and ODE’s. If the college were to purchase one of the upgrades for us as we use Sage with our students, who gets the benefits of the upgrade? Is is the individual students that are in an instructor’s Sage classroom or is it the collaborators on an instructor’s project?"
If you were to purchase just the $7/month plan and apply the upgrades to *one* single project, then all collaborators on that one project would benefit from those upgrades while using that project.
If you were to purchase a course plan for say $399/semester, then you could apply the upgrades (network access and members only hosting) to 70 projects that you might create for a course. When you create a course by clicking +New, then "Manage a Course", then add students, each student has their own project created automatically. All instructors (anybody who is a collaborator on the project where you clicked "Manage a course") is also added to the student's project. In course settings you can easily apply the upgrades you purchase to all projects in the course.
Also I'm currently working on a new feature where instructors may choose to require all students in their course to pay for the upgrade themselves. There's a one time $9/course fee paid by the student and that's it. At some colleges (in some places) this is ideal, and at other places it's not an option at all. I anticipate releasing this very soon.
Getting started with SageMathCloud courses
You can fully use the SMC course functionality without paying anything in order to get familiar with it and test it out. The main benefit of paying is that you get network access and all projects get moved to members only servers, which are much more robust; also, we greatly prioritize support for paying customers.
This blog post is an overview of using SMC courses:
This has some screenshots and the second half is about courses:
Here are some video tutorials made by an instructor that used SMC with a large class in Iceland recently:
Note that the above videos show the basics of courses, then talk specifically about automated grading of Jupyter notebooks. That might not be at all what you want to do -- many math courses use Sage worksheets, and probably don't automate the grading yet.
Regarding using Sage itself for teaching your courses, check out the free pdf book to "Sage for Undergraduates" here, which the American Mathematical Society just published (there is also a very nice print version for about $23):