From a copyright standpoint in the US, you can copy the glyph outlines of fonts (usually some form of bezier curve or in some cases bitmap) without violating copyright. They are completely uncopyrightable.

Most fonts though (TrueType and OpenType) have a hinting language in them which is code and it is copyrightable since it is computer software. This means you can't just copy DIN font files themselves and distribute them freely without permission.

You can however take the outlines from the font, recreate the hints manually and then distribute it.

That said, there are such things as design patents and of course, trademarks. Design patents aren't used too much, but do protect the design itself. Trademarks of course allow you to protect the name.