it's piracy because dlc isn't meant to be shared like that.
(see
http://us.playstation.com/support/useragre...rk_oct_07.html)QUOTE
8. GENERAL LICENSE RESTRICTIONS AND TERMS
Except as stated in this Agreement, all content and software provided through PSN are licensed non-exclusively and revocably to you, your children and children for whom you are a legal guardian (collectively for purposes of this section, "You" or "Your"), solely for Your personal, private, non-transferable, non-commercial, limited use on a limited number of activated PLAYSTATION®3 computer entertainment systems, PSP® (PlayStation®Portable) systems, and any other hardware devices authorized by SCEA in the country in which your PSN account is registered
Yes you can get banned for sharing your account as seen in their banning explanations from their knowledge center
http://us.playstation.com/support/answer/i....htm?a_id=1260#QUOTE
Share / Hijack Account
Sharing personal PSN account information in order to obtain access to another persons PSN account. Changing another persons email address, and/or password without their permission in order to gain and control access to an account. Offender attempted to use or take content they did not pay for.
As to why the mods don't care, it's best to ask them yourself.