[asteadman]

This would normally be the case, but for small projects with a small number of contributors, they are always free to dual-license their own code, even "retro-actively". Anything that was already released would still be available under GPL, but new edits could in theory be licensed under whatever terms they want, independent of how "derivative" it is. For large open source projects without a copyright assignment clause, this is essentially impossible, but for small projects it's relatively easy, assuming you can track down all the contributors. IANAL.