You typically do no need the approval or permission of co-authors to include your shared work in your thesis or dissertation.
For copyright purposes, joint authors are co-owners of the created work. This arises from shared intention that each author’s individual contribution be merged into inseparable or interdependent parts of a unitary whole.
Shared authorship in academic publishing practice may be broader: that is, contributors who only provided data or funding, or contributed ideas without actually writing or editing portions of the piece, wouldn’t be joint authors and co-owners for copyright purposes, but may nonetheless be included as co-authors under local or departmental practices.
When a contributor is a co-author for copyright purposes, each has an equal, undivided interest in the work. This means each can:
- Utilize and revise w/o other’s permission, and
- Grant non-exclusive licenses (i.e. could give another publisher permission to print and sell work without others’ consent—though this comes with the obligation to account to the others for any profits gained).
That said, it is good practice to inform co-authors where works are going to be distributed. It is possible that you may have entered into a funding or employment arrangement that would place copyright ownership with someone else. In such cases you should refer to your employer’s policy.
For more information, see Stanford's Fair Use guide regarding joint copyright.
