seanmcl, you are quite right your post does discuss DMCA. But the origination of this thread came about because of observations raised by Sean at OSXForensics website with respect to copyright.
trewmte My points were
1. It is hard to understand how the common methods of forensic jailbreaking would violate copyright law. I disagree with Sean Morrissey's application of the law in this instance and interpretation of it, based upon my experience in the application of copyright law to software. It doesn't violate Microsoft's copyright for me to install Cygwin or OpenSSH daemon. Why would doing the same for OS X be any different?
2. Jailbreaking might violate the DMCA, which prohibits breaking of DRM, but there have been exceptions and forensics would appear to be consistent with the interpretation of exceptions to the law.
Morrissey makes the claim that jailbreaking iPhone OS X violates US copyright law. I disagree.
For my part, I would welcome a memorandum of understanding between Apple, Microsoft, Google etc and the agencies involved in the forensic analysis of their devices and systems in order that people in our line of work dont have to worry about the implications of copyright infringement.
I would think however that the companies involved would shrink from allowing such an understanding and Microsofts attempt at helping LE with their COFFEE application is a good example of the damage that these organisations can be exposed to by such altruistic activities.
I do not think that any manipulation of a digital exhibit that allows best evidence to be acquired would ever be successfully challenged with respect to copyright infringement; as long as the sole purpose of such manipulation is in order to assist due legal process and not for personal gain.
Being 'forensically sound' is a term that some of us associate with not altering data on the evidential item, this is not always possible and therefore 'forensically sound' can mean acquiring the best evidence at the cost of altering some data on the evidential item (you must know what that is however!). This does have implications and will alter the evidence but in most cases will not alter the relevant evidence. In this case, 'Jailbreaking' an iPhone is forensically sound.
I have always thought that any mobile phone examiner takes his life in his hands when he turns on a mobile phone because he can not possibly explain or know what exactly will happen when he does so, however this is still accepted as forensically sound and so it should be.
A very interesting thread and I am pleased that the contributing members have posted in a very professional and constructive manner.