The conventions I'm using are to put the entire copyright notice at the bottom
of each file, and to put the summary of the source file's use at the top of the
header.
Putting the license text in each file avoids confusion, and is normal practice
for many projects. Putting it at the bottom gets it out of the way; it's a
ton of clutter to put at the top.
The description is in the header. People who don't know what a class is for,
or how to use it, are probably looking at the header to see the interface,
not the implementation, so let's put the description in there. Keep it brief
(one line); any substantial implementation notes should go in the source file.
Glenn Maynard