It's probably the course book that the professor or department wrote for the specific course because they couldn't find a textbook that covered the material they wanted in the way they wanted. A lot of courses at U of M had them in the 90s; you'd buy the course book from a local printer's shop as a tape-bound, soft-cover book. They were very nice because they covered exactly what you needed using the same language as the professor. It was like having notes you could read before the lectures.
Good question. I'm honestly not sure. I just stumbled across it while looking for linalg resources. It appears to be legit, since the author is with UPenn and it's on a upenn.edu site. But I don't see an explicit license notification or anything, so not sure if you're even allowed to print it out yourself or not.
