There's no crack for DarkTree 2 Demo. The Demo on their website
is savedisabled. It doesn't contain the save-routines. Since
the routines are not there, saving is not possible.
A crack working around that is theoretically possible, but it
would mean that the programmer of the crack would have to know
about all the internal data structures of the programm, and
also know the file formats used during Open, and would write
the Save Routines by himself, and somehow be able to integrate them into the demo.
I'm using my computer for quite some years ,I've seen a lot of savedisabled software, but I've never seen anything like that achieved, so its impossible as far as I'm concerned...