Today I was listening to Talking Drupal #168. The topic was how to ensure that open source project developers can afford to provide updates to their users. As an open source developer myself, I have to disagree with the premise that we should support a distinction between users and developers. The projects that I develop for are the projects that I use. As a user-developer, I do not care how many users a project has. I care how many user-developers it has.
Sustainability for open source projects does not mean that developers can afford to provide updates to users. It means that users provide updates themselves. All users benefit by avoiding duplication of effort. It helps if the primary developer of an open source project is also the primary user, because that makes the developer the primary beneficiary of user updates. A sustainable open source project must be designed to make user updates easy.
Open source developers who hope to be supported by user donations rather than by their own use of a project are missing the point of releasing a project under an open source license.