You have to look from two sides this
Moral: What is right or wrong? If they wanted to change the license, they could have made another project with another name, and nobody would care, but they wanted the reputation of the project.
Legal: How much are you willing to spend on litigation? The only real "protection" by copyright is in court.
Further, while the copyright of the original code and its derivatives are still owned by the original author does that hold true to the rights to the name and package namespace? Supposing this were indisputably a clean room implementation instead of an unclear one, would the maintainers then have a right to relicense under the same name? I would imagine that yes, they do have the right to relicense in that case because the copyright only applies to the code, not the project itself.
Other questions that haven't really been explored before also are maintained: the original author hasn't been involved in some time, technically the copyright of all code since still belongs to those authors who might be bound by LGPL but are also the only ones with the right to enforce it and could simply choose not to. What then?
Legal: How much are you willing to spend on litigation? The only real "protection" by copyright is in court.