MS-DOS v1.25 and v2.0 is now open-source (2014)
If I could pass my ideal version of copyright to the world, this is what I would dream:1. Copyright is 20-30 years in length, maximum. (We can argue about that.)2. For computer programs, a copy of all source code, build tools, and final binaries must be supplied in an offline format (maybe a Blu-ray Disc or a few?) to the Library of Congress to store, duplicate, and preserve as needed. This content will then be released on the copyright expiration, and the offline format is meant to render computer hacking ineffective for stealing the work. For software as a service that is continuously improved, new discs must be received yearly.#2, I think, already has precedent considering the patent system. A patent is meant to describe how to perfectly recreate the patented technology (minus, maybe, a few trade secrets), so why not copyrightable software?