As much as I like TS and consider it's interface, philosophy and workflow; I think yeah, it is nearing 5 years since it's EOL. It may be more efficient to build from the ground up a new system with similar concepts (with the support of a somewhat rich benefactor) with a team of taleneted people to incorporate trueSpaces ease of use philosophy right into a new product.
Right now
Fabric Engineis free for use up to 50 liscences, and it's a whole system built around KL, a python syntax C++ optimized code system, also built around nodes - that can be used to create interfaces and whole 3D platforms within other packages or as a standalone. It also has a DX11 viewport and GPU accelerated systems - to build a new "opensource" user friendly package like trueSpace - I recommend getting into that. it's free for up to 50 seats - and with that you can build directly into Maya, Softimage or Max, and they are considering splicing into other 3D authoring packages. If it could be spliced into Blender, that would be the ultimate opensource 3D package you could incorporate TS's philosophy.
It's very powerful, and more when you know Python and know what you want to do.
I do recommend you breakdown what is awesome of TS, and try replicate it or "splice" it into another package.
The coding platform of Fabric Engine is already created - and a lot of the tools (GPU enveloping and autorigging, cloth, particles, crowds, DOF, AO, procedural modeling, etc) have been done and left for free - and more you have a huge audience and market if you develop on that platform, as it works in most mainstream packages from Autodesk without having to recode anything.
So... break TS down, find out what makes it tick. Is it the icon interface? The floating button toolbar? The world/object/view orientation, Z up click and drag everywhere? Axis limit of the interface? The ability to move objects in world/object/view orientation without having to use the widget? The box with the gimble widget? The animation tools? The full body IK rigging with FK limits and possibilities? The LE with it's ability to edit everything scene wide from nodes? The realtime viewport - WYSIWYG type of work? The ease of use? The multiple viewports, the scalability and ability to modify the layout? What is it that makes this software tick, and how can you build your system to reflect or even better that philosophy?
Cloth, hair? TS was never fully developed, but the philosophy was nearly there. And it's great, and still very future proof concerning what it had in mind to be.
So yeah, maybe it would be worth getting into FE to build what you want as a standalone or as a spliced function in mainstream software - or even get onto developing trueSpace's philosophy into one very strong opensource app already out there, Blender. Put in a whole new Icon based interface, create a new way to manipulate objects, better the viewport, help develop node level editing of everything in the 3D space - work on full body IK rigging, easier widget based deformers (bend, twist, etc) any of that... cause it's opensource, you can, and it will develop down that area.
Decompiling a 5year old chunks od DLL's to then re-organize what is what to then document it then share it, then start developing it from Truespace will prove to be a huuuuge amount of hard work and time, and it will just get you to square 1 once all that hard work is done. Better start at square one with the design and philosophy of trueSpace for something much more easier to build with today's tech and code, GPU acceleration and optimized code.
And if you ever do get some kind of crowdfunding to make a TS gpu accelerated clone 2.0 - please update it's progress here on the forum, I'll support you, though I'm more artistic than a programmer...