Shakes,

I think I have your answer. According to their license on the website you can do anything you want with it as long as you strip any references to Project Gutenberg from it and the book is in public domain (as are most of their stuff). See the source link to find the whole license. Here is the applicable section:

"1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation"
or PGLAF), owns a compilation copyright in the collection of Project
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Gutenberg-tm License when you share it without charge with others."

If you use the Project Gutenberg name you have to follow certain rules. For instance you can't change the content or make derivative works. Those are also listed on the source page below.

Hopes this helps,
George

This is very straight forward, so don't worry. The restrictions about which you seem to be worried are when you wish to leverage the Project Gutenberg trademark. If you are looking only for the content, then you have tremendous leeway.

There are three parts to the Project Gutenberg license:

1. Your rights
   
2. Their limited warrenty
   
3. Use of the Project Gutenberg trademark.
   
   

This license applies to two different types of books:

1. Public books whose copyright has expired in the US
2. Copyrighted books whose authors gave Project Gutenberg permission to distribute the books.

So, at the core of this are the following issues:

1. Is the book in the public domain in the US and are you in the US
   
2. Do you want to use the Project Gutenberg trademark?
   
   

So, assuming that there is a book in the public domain and you want to put that book into a different file format, which will not change the contents of the book, then, according to paragraph 1.C of the Project Gutenberg license, they will "not claim a right to prevent you from copying, distributing, performing, displaying or creating derivative works based on the work as long as all references to Project Gutenberg are removed."

This means that you really can do what you want with it. Even to the point of creating derivative works, such as writing a story based upon Shakespeare's characters (you couldn't do that with J.K. Rowling's characters).

The situation is different if you are outside of the US, or if the work was granted to Project Gutenberg and is not in the public domain. But you indicated that the work in which you are interested is, so it seems you are clear to go.

Straight from the license page: "If you strip the Project Gutenberg license and all references to Project Gutenberg from the ebook, you are left with a public domain ebook. You can do anything you want with that." This only applies to books whose copyright has expired in the United States, not when the author has given PG the permission to use it.

I see no problem with what you are describing, nor would you need to make your work available under the same license. It is only when one would want to use the Project Gutenberg trademark that you have to pay royalties (if you would charge) and are only allowed to distribute verbatim copies.

Complex question. In pure terms public domain means you can use it any way you want. Project Gutenberg does offer some copyright protected works that people can download and read but the authors still maintain copyright which prohibits you from selling those works. For Shakespeare I'd take an educated guess and say you should have no problem; but you need to consider the copyright laws in your own country if not in the US because Gutenberg doesn't deal with any other countries' copyright.

Bottom line though if it is in the public domain you can do anything you want with it.
For instance this one you could do anything with: http://www.gutenberg.org/dirs/etext98/2ws3010.txt