I recently forked an open source project that is licensed with the LGPL license. This fork quickly turned into a complete re-write of the project from scratch. While the concept of the project remains, no original source files have been saved. What I would like to do is license my new library under the BSD license (3 clause) but I am a bit fuzzy on the terms. I am aware that I have to license modifications to the original in the same license but what constitutes a modification? Thanks in advance for your help.