As always, it depends. 
But I think, as a general rule of thumb the following parts of the rules could be helpful:
If you can honestly say to yourself, “Yes, I mainly used Blender to make this”, “Yes, nearly all of the foreground models are new”, “Yes, most of the models are new”, then the entry is Pure.
So basically, just take into account all the software that was used to create the entry and how big blender’s part was in the end.