"DJ Friendly" extended mixes generally extend the beats and or bass lines of a song so that the beat and or bass line can be introduced before the main part of the song comes in.
for example, the following link is the radio edit of Above and Beyond's Sun and Moon
Sun & Moon (Radio Edit):
http://youtu.be/ll5ykbAumD4compare that to the club mix of the song:
Sun & Moon (Club Mix):
http://youtu.be/zWxsn8c6GLQthe extended club mix will allow DJs, like me, to loop the beginning of the song and introduce it subtly while the other track is still playing. Thus extended or club mixes are, DJs firendly
the term DJ friendly isn't throw around often (or at least I don't see it much). The first time I've seen it is on a Deadmau5 album:
