I'm beginning work on a project which I may wish to commercialize in the future. For now, though, it's just a prototype which I would like to release it with a GPL license.
My concern is: if I am to receive contributions (code patches, artwork, etc) toward the prototype open source project, I don't want to be faced with the task of trying to determine which parts of the project I can and cannot use in the future commercial version.
To this end, my preference would be to license my prototype version with the GPL, and require that any contributions made to the project are either in the public domain or licensed according to some attribution license such as the BSD license. (In the event of a future commercial product, I don't mind giving blanket attribution to anyone who contributed to the prototype version).
Is this a realistic thing to do? Are there examples of other projects doing similar things? How has this been met by potential contributors and/or users of the projects?