Dark GDK - Product developed by TGC. It's a C++ Library designed for making games.
Dark GDK.NET - Product developed by ApexNow. It's a .NET wrapper of Dark GDK, but you can only use it in C# and Visual Basic.
Dark GDK 2.0 - Product developed by Mistrel. Originally it was for Pure Basic under the name of Pure GDK. Mistrel developed version 2 to create a version of the Dark GDK library that'll work with a number of languages, including C++, C#, Pure Basic and Visual Basic. It was rebranded Dark GDK 2.0 because it was no longer specific to Pure Basic.
Dark GDK 2.0 seemed like it would make other versions of the GDK obsolete as it covered all the previous languages and more and of course it would be up-to-date with the latest DBP libraries. Unfortunately Mistrel is MIA. This is why I went ahead and bought Dark GDK.NET and didn't wait around for him to return. It's a really cool project and I hope he's not gone for good.