According to its homepage, the SemWeb library (great library for handling RDF under .NET) is released under GPL. Since the ROWLEX tool is built on SemWeb, ROWLEX supposed to be GPL, too. Still, ROWLEX is claimed to be released under L-GPL. Is this legally correct?
Actually, your statement is not completely accurate. SemWeb is not just GPL but dual-licensed. The source code written by Joshua Tauberer is also licensed under Creative Commons Attribution license. Since ROWLEX relies solely on the code Joshua wrote, the Creative Common Attribution license permits ROWLEX to be distributed under L-GPL.