Is this against the rules?  Does anyone do this?  If it is okay, where would I post such a request?

Yes it is against the rules. You can sell credits for money or exchange them for books. You can trade them between the sisters sites (swapadvd, swapacd) but you can't trade them for pts for another club. 

As a member of bookmooch and pbs, I can't imagine anyone wanted to trade PBS credit for bookmooch pts.   I'd rather have more credits here than there.

Yeah, I'm realizing that I should've used this site from the beginning.  My favorite part about Bookmooch is when I go to request a book and the last time the user has logged in is 337 days ago and they are possibly inactive.

I use both sites. But I never let more than a few credits build up on bookmooch.  It's not always a reliable site as far as being able to access your account.  And the lack of rules makes it hard sometimes. Like right now I have a book I requested from there in January that was accepted but still hasn't been mailed.  I see that they log on regularly. They accepted the request.  But they haven't mailed it yet. The only reason I haven't cancelled it is because it's an out of print book that is very rarely posted here and has been on my WL here for over 2yrs.  If I happen to get here before they mail it then I'll cancel. 

I do trade some books there when I have a heavily posted to PBS book or a damaged but still readable book.  But I'd prefer to trade books here.

It's actually OK to trade bookmooch for PBS credits BUT you have to do it in a specific way:

Post in the Book Bazaar that you want PBS credits and to pm you to get more info.  This way, it's done in a private transaction.  PBS is OK with this - as long as you're not posting the details in the public forums.

ETA:  I found this:

Date Posted: 10/12/2007

All right, here is the PBS Team word on this.

You can sell your PBS Credits here.  (And this should be done in the Book Bazaar, not this Forum.)

You cannot sell anything else.

That means that [removed name], you could have posted "Anyone want to sell me some credits?  Contact me by PM if so," and then in Personal Messages explained what you are willing to pay.  But you should not post a topic selling anything for credits.  If in PM negotiations anyone was willing to accept the currency of another site for PBS credits, then you could make the exchange.  

It is a small point, but there you have it.  Don't hawk your wares (whatever they are) for credits.   But you can ask if anyone is looking to sell credits, and negotiate payment with them privately.

We are sure someone else will find a way to do the above inappropriately somehow, and we will hear from members again asking us to clarify, but for now this is the ruling.

PBS points are hard to acquire.  I don't know why anyone would want to voluntarily give up PBS points.

I use bookmooch mostly to acquire heavily posted books that I want, and to give away damaged books that I also offer here as unpostables free w/ order. Occasionally a WL book will pop up on bookmooch and surprise me (I scored a like-new copy of "World War Z" on bookmooch just by keeping an eye on my WL there! I was shocked.) and then I'm grateful for the points I accumulated there. I have a friend who has, in the past, traded me PBS points for bookmooch points. We've only done it a few times, and I was extremely happy she was willing to do it. For her it doesn't really make a difference; she has this magic touch and gets great books from both sites by making connections with the other members.