As a user of IPCop, you are allowed to use the software in any way you wish and can even redistribute it, even modified, if needed. The software can be taken in another direction much like IPCop's own creation where it was forked from Smoothwall. This ensures that the software stays around and is useful for years to come, as you can be confident that there will be enough users turned into developers to keep the project going.
You can take the knowledge gained in this book and use it to create the network device that fits your specifications and modify and tune it as necessary. There are options and choices and the software has the protection of the GPL to allow it to survive any issues it has. This means that you can be quite confident in the choice of software as your network doesn't rely on a corporation staying afloat but rather on thousands of users and developers around the world, showing that they can and will work together in order to create truly remarkable software.