Hello I got a question

Hello I was just wondering because I saw some RP's saying that if you want to make an RP then you have to ask permission by someone.

go here for unhosted http://www.killermovies.com/forums/showthread.php?threadid=360856&pagenumber=1

here for regular rp
http://www.killermovies.com/forums/showthread.php?threadid=374589&pagenumber=1

and here for star wars
http://www.killermovies.com/forums/showthread.php?threadid=5187&pagenumber=1