It's the original spirit/sentiment behind patent law and copyright law. Copyright sort of lost the thread on that one over the course of its extensions, but in the case of the book the "source code" to construct the book is very similar to the contents of the book and a limited copyright term was supposed to imply that eventually the public would have access to it after the brief monopoly rights granted to the creators of the work.

As copyright pushed to things beyond books that also made it easy to forget that original "open source" idealism behind copyright. It's tougher to build a new movie out of the components of a published movie than to build books from the components of published books.

Patent law is where the idea was applied to something that needed "source control preserved": describe an invention in complete detail in a public registry so that others can recreate and get a powerful limited monopoly on it, but as soon as that limit hits everyone should be able to recreate it.

Software patents have long been a mockery of that original spirit of patent law, but "open source projects by companies get stronger piracy protection/what have you for the first X years of their registered life" is really what software patents should have been in the first place, based on the original goals of what patents were for.