[niccaluim]

It's got nothing to do with copyright. Classic Mac OS, from which HFS+ descends, happily copied both forks of a file for you. I'd be shocked if OS X's Finder didn't also copy both forks. I believe cp also supports them. And you can access them on the command line by appending "..namedfork/rsrc" to the filename.

Although resource forks were just another data stream at the filesystem level, the OS treated them as structured data, with record types and IDs. They were used to store user interface elements--icons, pictures, window definitions, dialog boxes, etc.--as well as string lists, version information, and, yes, fonts. Even the executable was stored as a resource (M68k code that is; PowerPC binary was in the data fork). Applications could define their own resource types too.

As another poster points out, this scheme helped applications manage memory by only loading into RAM the resources it actually needed at any given time.