Otro libro oficial de Blender the essential Blender

Todo está perfectamente legal.

No parece legal. Han borrado el texto con la licencia, cuando el autor explícitamente indica que es necesaria su inclusión.

Vaya, la gente no sabe copiar ni cuando el material es libre y gratuito.
1. You may copy and distribute exact replicas of the opencontent (OC) as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty.

Keep intact all the notices that refer todo this license and todo the absence of any warranty.

And give any other recipients of the OC a copy of this license along with the oc. .