See the question and my original answer on StackOverflow

CodeFluent Entities is a custom-made tool, it's not relying on any 3rd party software. The graphical surface is using WPF with special algorithms and specific lightweight treeviews. (disclaimer: I work for this company, and I helped develop that software).

That being said, if you want to quickly develop something, you could indeed start with the you mention (VSVMSDK is the successor of the DSL SDK, aka 'DSL Tools'). It has the big advantage of being free. Note however the future of this component at Microsoft is unclear, as they seem to prefer 'Code-first' over 'Model-first' now.