(In the following, assume that "I" is not personal, but could be a corporation or group suitable in size and training to perform the tasks)
I have received sample code carrying a license patterned after BSD:
Copyright (c) (Year and original author are specifically named here). All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
Neither the name of author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
The significant deviation from the "classic" three-clause BSD license, as seen for example on Wikipedia is that the disclaimer uses the phrase "AUTHORS OR COPYRIGHT HOLDERS" instead of naming a particular entity.
Assume that I take steps to ensure quality of the final version of the software I develop using this BSD-licensed source code, such as code inspection, testing, use of static analysis tools, perhaps even going so far as formal proofs of correctness. (Ignore for the moment that compared to these costs, recreating the software from scratch is probably feasible)
May I now offer the final version to a client under terms that extend warranties disclaimed in the original BSD license, such as fitness for a particular purpose? Due to my quality assurance process, I am expecting to assume the associated risks, and hold harmless the authors who gave sample code to me.
Or does the license disclaimer, which I must preserve intact under the terms of redistribution, fixate the agreement between myself and my customer to the same "as-is" terms that governed the original sample, because that disclaimer names "COPYRIGHT HOLDERS AND CONTRIBUTORS", a category into which I now fall?
Is it permissible for me to substitute the name of the actual entity in place of references to that entity such as "COPYRIGHT HOLDERS", "AUTHORS" or "CONTRIBUTORS"?
Does the answer change at all if the quality assurance and warranty are provided by a separate entity who has not contributed to the software itself?