Go ahead. You do not need permission to distribute anything we have released, so that you can master your CD as soon as the beta-test ends. You do not have to pay us anything. We will, however, publish a list of CD manufacturers who donate money, software, and time to the Debian project, and we will encourage users to buy from manufacturers who donate, so it is good advertising to make donations. Of course all CD manufacturers must honor the licenses of the programs in Debian. For example, many of the programs are licensed under the GPL, which requires you to distribute their source code.
Yes. While all the main components of Debian are free software, we provide a non-free directory for programs that are not freely redistributable. CD manufacturers may be able to distribute the programs we have placed in that directory, depending on the license terms or their private arrangements with the authors of those software packages. CD manufacturers can also distribute the non-free software they get from other sources on the same CD. This is nothing new: free and commercial software are distributed on the same CD by many manufacturers now. Of course we still encourage software authors to release the programs they write as free software.
Yes. For example, one person is building a "Linux for Hams" distribution, with specialized programs for Radio Amateurs. He is starting with Debian as the "base system", and adding programs to control the transmitter, track satellites, etc. All of the programs he adds are packaged with the Debian package system so that his users will be able to upgrade easily when he releases subsequent CDs.
Debian also provides a mechanism to allow developers and system administrators to install local versions of selected files in such a way that they will not be overwritten when other packages are upgraded. This is discussed further in the question on diversions.
Go right ahead. The package tool is free software.