Prior to the Copyright Act of 1976 (which, confusingly, only went into effect in 1978) the copyright rules were different. One of the things that was introduced was that after the beginning of 1978, software could be explicitly copyrighted.
So, what about software which was published before 1978? I've seen a variety of opinions.
- that it can't be copyrighted at all.
- that the representation of the software can be copyrighted. For example, a magnetic tape containing the program. But the program itself can't be.
- that the source code, being a literary work, can be copyrighted, but the object code which can't be read by humans can't be.
- that it works the same way as it does today (although with an expiry date of publish + 28 + 28 years).
The reason why this is interesting is that it may or may not make pre-1978 software public domain in certain circumstances, even if it was published with a copyright notice.
Does anyone actually know about any of this? Finding information on pre-1978 copyright is like pulling hen's teeth.
softwareandcopyrighttags, including possibly two in the following query that may cause this one closed as a dupe: law.stackexchange.com/search?q=software+copyright+1978