[quote=@SleepingSilence][/quote]

I don't think it's a matter of getting permission really. Because obviously it's on the internet and they put it up to get exposure and they're very aware people will save/download/repost whatever. Yes they've put their copyright notice on it in terms of someone not stealing the work to resell. 
Its more along the lines of if the original artist finds out that their work is being used on another website and decides not to take legal action and instead requests that the site mod/admin takes it down then they take it down.