Background thinking around this question: There are instances of OSS users levelling expectations at OSS maintainers that they provide a certain level of service, whilst OSS maintainers generally have no obligations to users. Jacob Tomlinson provides a good summary and discussion of this issue in “Don’t be that open-source user, don’t be me”.
Existing terms: The term voluntary is often used to describe OSS contributions, and contributors referred to as volunteers. In particular, these terms are sometimes used to remind users that maintainers aren’t generally obligated to do anything in particular. However, I find that these terms don’t always accurately convey the nature of contributions, particularly when contributors are employed to work on them – the idea of a volunteer can carry the connotation that any contributions are made in free time, or that no reward is being received for them.
An alternative: Discretionary contributions are those that are left to the maintainer’s choice or judgment – there may be remuneration for their work, but in terms of the relationship between the user and the maintainer, there is no particular obligation. In these cases, is discretionary contribution a more appropriate term than voluntary contribution?
Graham Markall 