From below, but I feel this may pop up for some of the self employed folks on this board.
I sent a copy of the so called agreement to one of my best general contractor clients I've ever worked for and asked the same questions "...WTF is this all about..." He passed it on to his head bean counter and she suggested I cut bait and run. She had never heard of such a thing. I'd had already figured that as my battle plan, but thought I'd get some other opinions. This includes beerleggers and a trusted general contractor.
I think I attached what they sent me to sign. Please disregard the contractors name, ok (it's invisible, but my white out may have got sunburned....)
Never mind, I guess I can't load a pdf image file. I'll try and make it a jpg file if anybody cares.
I'd love to see it. and no I would not sign it. I would tell them that before I even looked at it, every dime owed was paid. then after they paid, I would look at it and say no.