[yummyfajitas]

Problem set quality is not the issue. If it were, I would donate a week or two of my time and build a problem set generator.

The issue is that you need the same problem sets as the instructor. If the instructor uses Stewart and homework is graded, you get a 0 on HW. This is why you can't even go back 1 edition of the book, and why the legacy publishers print a new edition every 2 years with minimal changes beyond tweaking the problems.

A startup idea I never pursued, but one I think has a lot of merit: build an online problem cross referencer. It provides a) free problems to any instructors who want to use them and b) crossreferences these problems with existing textbooks (that way students who don't want to buy the book don't have to).

I'm pretty sure that Int[ 1/Sqrt[3+5x^2], {x}] can't be copyrighted.

[pixcavator]

Int[ 1/Sqrt[3+5x^2], {x}] can't be copyrighted but a problem set that consists only of exercises as routine as this would be almost worthless. A cross referencer is a neat idea though.