For the Ali Nadem and Nilow songs, all you've got to do is put their name in the tags,description or anything else. If you do that, you are free to do whatever you like with the video (We even said this in the description on our video)
For the DotEXE remix, its uploaded on various partnered youtube channels who all state its copyright free.
Also:
"Because remixes may borrow heavily from an existing piece of music (possibly more than one), the issue of intellectual property becomes a concern. The most important question is whether a remixer is free to redistribute his or her work, or whether the remix falls under the category of a derivative work according to, for example, United States copyright law. Of note are open questions concerning the legality of visual works, like the art form of collage, which can be plagued with licensing issues."
If its a true remix, you do not need permission from the original artist. From that point on it becomes intellectual property; the same as copying an article from a website to another, articles are intellectual properties
"There are two obvious extremes with regard to derivative works. If the song is substantively dissimilar in form (for example, it might only borrow a motif which is modified, and be completely different in all other respects), then it may not necessarily be a derivative work (depending on how heavily modified the melody and chord progressions were)"
Dubstep remixes are mostly non-derivative works because they change the pass, the bassline, the synth and all other dubstep wiggles you can get, and therefor the artist who remixed a song does not need official permission from the original author. Most of the time that is.
As i said, google it. You'll learn more than you could ever imagine!
Oh and before you start asking about where i got all this intel. Its a mix from a wikipedia article and the "Fair Use" law from the US.
To be honest, i would've never thought i'd have to explain the reason why a remix can be considered the "original" or "Non-copyrighted" on a Dubstep forum.
Sources:
http://www.copyright.gov/fls/fl102.html
http://en.wikipedia.org/wiki/Remix#Copy ... plications
None of the original artists will care, but you're misleading people