Well, some scumbags in the past have uploaded the hard work of the members here to e.g. the Kobo store, and tried charging money.
But other than that, you should be fine.
Accreditation is always good.
Note: Most books in the MR Library are Public Domain, but they don't have to be. I believe that the rules allow someone to upload their own work -- and then MobileRead is naturally permitted to distribute, but others are not.
As HarryT said, just because something is PD according to the rules & location of the MR Library, does not automatically mean it is PD in your location as well. But that is not a MobileRead-specific problem.