The actual code of a font (ttf, otf, whatever) is copyrightable. The shape of a font isn't, and AFAIK it isn't protectable by any form of IP. This means that while you can't redistribute or embed the TTF you got from a type foundry except as specified by the license, you are free to use it to create a near-perfect knock-off that doesn't share any code. This is where the fonts on all of those "Free Fonts" websites come from.