The law on Fair Use is of international magnitude with the arrival of the Internet. More on this in Part 2. It is a technical infringement to copy or prepare derivative works of, distribute, sell and in other ways deal in a quantum of another's copyrightable materials without permission. How much, when, for what purposes and whether for charity are all defined by the fact pattern. It is always best, if needed, to have written licenses to use other's materials.
Technology constantly challenges the laws to make the best sense of it all.
Unfortunately, like all other things in cyberspace, fair use is changing. The law in its raw form is cited as 17 U.S.C. Sec. Hundreds of cases discuss this requirement. They are not intended to be the only purposes. The factor that the potential market is altered may not be considered if the work is not published and trade secrets law may apply to further protect such a work.