Actually, the terms found in "shrink wrap" licenses tend to vary to some extent (at least in the US), so for any given bit of software what is and is not permissible may be different. I have seen some which explicitly permit you to make 1 copy of the software for backup purposes only, but that is by no means universal.
"Shrink wrap" licenses have always seemed to me to be, shall we say, less than fully ethical in their terms. While it is possible that if you were to challenge the terms of some provision of the license in court you might actually win your case, you'd probably have to first find yourself in a position where the publisher was actually attempting to enforce your violation of those terms before any court over here would even consider taking up the matter.
As for what happens to a copyright in a case where the company that publishes a bit of software goes under, in the US at least the copyright does not revert to the programmers (and except in very rare cases, it never was theirs to begin with). Software is considered to be the intellectual property of the company, and when the company goes under, the copyrights remain a part of the assets of the company every bit as much as the tables and chairs in their offices do. Those assets may be sold or signed over to others in an attempt to at least partially offset any of the debts owed to creditors, so the only way that the rights might be given back to the programmers would be if it was determined that the copyrights were of little or no value to anyone else. You could easily argue that the copyrights for much old software are of little or no value, however the owner of the copyright still has to give up those rights. While the company is actually going through the bankruptcy process, even that would probably require the approval of a judge.