From The 1709 Blog:
In the Florence Foster Jenkins decision, as discussed here, Hacon J gave a useful summary of UK copyright law on the issue of joint authorship. The summary, as set out in para. 54 of the judgment, almost reads as Hacon’s ‘10 commandments’ on joint authorship under UK copyright law:
“(1) A party will be joint owner of the copyright in a work only if he or she (or in the case of a company, its employees) collaborated in the creation of the work. The collaboration must be by way of a common design, i.e. co-operative acts by the authors, at the time the copyright work in issue was created, which led to its creation.
(2) The contribution of each author must not be distinct from that of the other author or authors.
(3) Contributions by a putative joint author (including those done by way of collaboration) which formed no part of the creation of the work are to be disregarded in the assessment of joint authorship.
(4) No distinction is to be drawn between types of contribution that did form part of the creation of the work. In particular, there is no distinction which depends on the kind of skill involved in making the contribution.
(5) The contribution, assuming it is relevant to the assessment of joint authorship, must be sufficient. This depends on whether the contribution constitutes a substantial part of the whole of the work in issue.
(6) That will be the case if the contribution would be protected by copyright in the work. Thus, if the contribution alone were copied by an unlicensed third party and such copying would result in an infringement of the copyright, the contribution constitutes a substantial part of the whole.
(7) The test of substantiality in the context of joint authorship of copyright, as in the context of infringement, involves a qualitative as well as quantitative assessment.
(8) Suggestions from a putative joint author as to how the main author should exercise his or her skill – for instance by way of criticism or editing of a literary work – will not lead to joint authorship where the main author has the final decision as to the form and content of the work.
(9) It is thus relevant, but not decisive, whether an author is the ultimate arbiter as to the content of the work.
(10) If joint authorship is established, the court may apportion ownership of the copyright.”
Link to the rest at The 1709 Blog
The OP includes links to a number of other copyright case opinions discussing joint ownership.
PG says this is relevant for authors, including indie authors, because it is not unusual for more than one person to contribute to the creation of a manuscript. One may create the bulk of the first draft. A second person may produce a major rewrite of that first draft into a final draft that leaves only a tiny fraction of of the original draft untouched.
In a perfect world, spouses would never divorce or separate, friends would never experience a falling out, etc.
If the revised manuscript is forgotten or ignored or generates less than $1,000 in royalties, the issue of joint ownership of the copyright will likely never come to light.
However, if the manuscript becomes a bestselling book and a movie follows and one of the participants in its creation doesn’t see any money, PG says, after years of observing human nature in action in the legal arena and otherwise, there is a reasonable likelihood that one or more attorneys will be invited to a party no one ever thought about.
It’s not terribly difficult to put together a short and simple agreement that specifies who will own the copyright to a manuscript created with material contributions of two or more people.