Language and automata textbook, free or low cost? I'll be teaching a standard undergraduate class on languages and automata next semester, and would prefer to use a legitimate free or low-cost text. Any suggestions?

I love the Sipser text but the latest edition costs $196, which is hard to say with a straight face in the age of free courses.
Maheshwari and Smid's Introduction to Theory of Computation is free, with a Creative Commons license. It has some computability and complexity theory as well but seems to be primarily on languages and automata.