There are more examples for this (Score 2, Insightful)

Hi,

it is not just WebGUI. There is more free software
that follows the "free source - payed documentation" scheme:

- jBoss is a free application server. However it is
hardly usable without the documentation which is
not free.
There is a free documentation project, but it
is available only for outdated versions.

- Blender is a great piece of free software but
trying to work with it without documentation is
a pure waste of time.
(However, I am not sure whether this is a
business model in this particular case.)

- OpenGL and other libraries are open to use but
require documentation in order to be used.
(Here You have to buy the book.)

- gcc is free. Learning C without a book or
teacher is nearly impossible.

What I want to tell You with this examples is:

- Not everything which is for free to get can
also be used for free.

- It is not a bad thing [TM] to give away the
source and keep back the docs.
However, if You do so, You should make clear
that You have to buy the documentation to
use the product.

- You have no right for free documentation.
(hard, but true)

- Any documentation which is not part of the
free product can be distributed with a separate
license. Therefore, it seems OK to me that
there is a nda for a installation guide.

- If it is really important, someone will figure
out the needed information and distribute it
for free.

However, stating that a product is completely
free to _use_ should include a free and good
documentation for the product.
Providing commercial support is another story...

Greetings, /.er