If somebody has participated in an open source project, and has previously contributed several lines of source code but all those lines have now been completely rewritten and/or deleted so that all earlier contributions by that person have been effectively erased, does that person still hold copyright on the derivative work?
I.e., certainly a full rewrite of a project will assign all copyright to those who have contributed to the rewrite only, but does this apply to individual contributions within a project as well?