The benefits of developing using an open source model don't need to be argued again here, I'll assume you are aware of them. What if other developers or projects decided to adopt this attitude? Where would The Dark Mod be then? This is not a rhetorical question. We all stand on the shoulders of giants when it comes to the tools, libraries, textures, etc., which are open for all to use, benefit and learn from. Why would The Dark Mod choose to stand aside?