The user gets only one chance at the copyright notice, mainly because it hides a random number generator which ensures that different demonstrations will be proffered every time the program is executed.
Whereas the authors reserve commercial rights to the programs, they place no restriction on copying for private use or study, save for insisting that the programs be copied in their entity, without any alterations whatsoever.
Naturally the availability of the source code will allow interested persons to correct errors or adapt the programs to their own requirements; general usage suggests that the code be annotated accordingly, and treated with the same respect as the original. The authors will, of course, appreciate being informed of errors, suggestions for improvement, or ideas concerning the coverage of additional topics.
The apparent conflict between ``no alterations'' and ``make your own corrections'' is easily resolved. Sometimes the only change made to a program is to remove or to change the attributions concerning its origin; this is not considered fair, and should be avoided when reproducing any program.
