Hi, do you know that there is a tutorial that explain how make a game like space invaders in this site ? 
I watched that videos and i download the models. Then i reproduced that game for android and i added the Highscore…
Can i publish that game for free, or because there is the free tutorial i can’t do it ?
If i can, how can i publish and where ?? 
Where can i read the licence of the game ?
Thank you
I think all the samples are free for you to reuse, but the right thing is to look for the license that came with the demo.
More to the point though, I kind of doubt anyone is going to download a little free sample just because you added a high score, let alone pay for it.
Read the license of the demo, and also, when you publish, do write a description stating the original sources and giving credit to them and don’t try to make any commercial use of it.