> If someone marks their software with a copyright message it's > copyrighted
> period.  

No, if it was fixed in tangible media after 1988, its copyrighted, regardless of whether or not there is a copyright message.  (This is true for most, but not all countries).

>Once you gain access to copyrighted software you > cannot do anything
> with ANY part of it without express permission.  

Not so!  You can make fair use, and you can take any non-protectible elements.  Further, you can do other things, pursuant to 17 U.S.C. section 117 in many, but not all cases.  Further, consent can be implied as well as express.  But this is all hazardous and fuzzy territory -- do not try to make these decisions unaided by competent counsel, probably a software specialist.

> You can't > use any part of copyrighted software regardless of how much > you change it or how small
> a piece without express permission.  

No, this isn't so.  Size CAN matter for purposes of fair use.  But the author's advice is far more often going to be right than wrong.  Always ask a lawyer if you are relying upon a fair use or implied consent theory.

> "based on" messages mean nothing
> and are only a courtesy (unless the author requires it as part of his
> permission).

This is absolutely true in the US.  Outside the US, however, the failure to give credit can be a violation of so-called "moral rights" or "droits moral," which are actionable protections given to the AUTHOR of the program independent of the copyright in many EC and other countries.  International publication without due care for clearance of IP is a risky business these days.

> Further, you can't distribute (give copies) of any part of > any software you
> don't have rights or permission to.

This is mostly correct.  A copyright owner's exclusive rights does include the exclusive right to distribut.  However, some copy-giving can be blessed under some circumstances -- another "do not try this at home" issue.

Again, please do not take this as legal advice for any particular matter.  Each of these issues are highly fact-specific in terms of their results, and subtle differences in facts can swing a decision 180 degrees.  Rely only upon advice of competent counsel who has studied your particular facts and applied the applicable law to those facts.

Hope this doesn't ruin anybody's day.
Best,
A