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Anon's comment opens a very interesting topic in my humble opinion: the copyright of lecture notes. As a math reader myself, I make perfectly clear at the beginning of my courses that all the class material can be copied and distributed freely, as long as there are no commercial purposes. I have always imagined that the same goes (by defect) to all lecture notes material. After all, they were created to be told and spread. However, examples like Grothendieck's reaction to the English collaborative translation of some of his foundational work shows us something different can occur.
The first proof I know of this fact goes back to Laska & Lorenz (J. Reine Angew. Math. 355 (1985) 163-172). They proved that there were at most 31 possible torsion subgroups, and then Fujita showed that there were in fact only 20. Unfortunately, I don't have the paper around right now and I can't recall if their proof of finiteness is easy or not (in fact they might even refer to a previous paper, you know how this goes...).
