"Or otherwise"... I wouldn't accept it. In contracts we signed, we acknowledged that there could be additional governing documents by including language in the master agreement which states:
The Agreement entered into between the parties will consist of the following documents collectively referred to as “the Agreement”
A. This Formal Instrument of Agreement
B. The General Conditions
C. The Statement of Work
D. Confidentiality Deed, Security Statement & Policy Commitment to Ethical Conduct attached hereto
In the event of any inconsistency between the various documents referred to above the terms and conditions of the documents shall take precedence according to the descending order shown above.
Sounds to me like some twit inserted the "or otherwise" on a whim.
But also, liability for what? I signed contracts with indemnity clauses in them, were I cause physical damage or death due to my negligence, that software and methodologies used were mine to use, and that I was responsible for my own taxes. My agreements also said, "Neither party to this Agreement shall be liable to the other for consequential loss."
If they are trying to imply that you have to pay for a failed project, I wouldn't touch it. Too many factors exist in any complex project that are out of your control. If I screw the project up, they can terminate me, they can refuse to pay me, but they can't assign the costs of a failed project to me.