Hello! Please check out the license file that you find inside each project to check out what you can do with them!
For example, the Hero project license.txt states:
Copyright (c) 2014, XDTech
The project file and images in this "Hero" project are provided for
demonstration purposes only and may not be redistributed for any reason nor
used as the basis for derivative work.
and the Dragon's one:
Copyright (c) 2013, Thiago Brayner - www.thiagobrayner.com
The project file and images in this "dragon" project are provided for
demonstration purposes only and may not be redistributed for any reason nor
used as the basis for derivative work.
Therefore you can't use these two. Other projects such as the Alien one allow more options (:
