GPL and nib files

[Jesse Hammons]

The GPL states:
"For an executable work, complete source code means all the source code
for all modules it contains, plus any associated interface definition
files, plus the scripts used to control compilation and installation of
the executable."

My question: does a GNUStep or Cocoa .nib file qualify as an "interface
definition file?"  I am confused in the sentence whether the "interface
definition file" refers to interfaces for object code (i.e. header
files) or whether it refers to Graphical User Interface definition
files, such as Windows rc files, Mac rez files, (icons, etc), or
cocoa/gnustep nibs.

On a related note, are nib files considered code or data?  I am making
an application that runs on GNUStep and Cocoa.  The code for this
application is GPL (because I am using someone else GPL code for part
of the functionality).  I would like to restrict distribution of the
nib files (which were created by myself only).  I am wondering if this
would  violate the requirement for distributing "complete source code."

What about images, sounds, icons and similar types of materials?  If I
combine GPL code with proprietary data, and ship resulting binary, is
that a violation of the GPL?  If I provide access to the source code
for a version of the application that is completely equal in
functionality (same code) but uses generic images does that qualify as
being the "preferred form of the work for making modifications to it?"

Thanks,
-Jesse

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