If the projects are posted as examples on how to do something then yes.
There are some caveats. There may be media, images, sounds, video included that are only used for example purposes and in many cases should not be used for commercial or the wider web (including personal use) etc with out the copyright holders permission.
Most code we post up is being put up in the knowledge that we are putting it here for reuse or to be altered.
If you see that someone has only posted a project so they can get help with it then think twice and ask before you use any of the materials. In many cases these should only be projects that they are happy with people seeing and probably using items but not all, so IMO it is best to try to distinguish these and ask for permission if you want to use something from them. Code or ideas that we offer to enhance them should not be a problem. Remember I am mainly talking about included media.
So from what I see in the link there should not be a problem you using and altering said project.