The requirements for applying to be a merit source happens to be that such individual must at least be somewhat of a reputable member on the forum,with at least some positive trusts and no negative trust(it will help increase ones chances),and also to garner from around the forum 10 posts that haven't been merited,or haven't gotten the real number of merits it actually deserves...

There is no tag as to a paid signature campaign,as it's absolutely acceptable on the forum,and being on one doesn't make one dishonest,or less trustworthy...
It's a honest way to earn from the forum, just that most noobs abuse it by spamming the forum with tons of alt accounts,and definitely the OP isn't one of them...

Good luck mate!!!