There is no particular obligation to credit your sources for chords. For one thing, you don't necessarily know where the person on Mudcat(or whereever) got the chords from. You don't even know if they are the right chords, and from my years of experience, the chords posted here and other places usually need some adjustment before they are workable.
If you include chords (which you really should), you need to make sure that the chords actually work--I would recommend that you get a collaborator who plays guitar to go thru all the chord progressions that you find to make sure that they are useable, and that they are presented in a form that they are easy to read and play-then you should then give that person credit. They will have earned it.