> Few further testing on GUI application under windows: tcl
> based application throws same error as tk based application

You still need to install TK itself on the second machine. TK
is not part of Ruby and, as such, is not embedded by
RubyScript2Exe. The bindings between Ruby and TK are part of
the Ruby environment and are embedded by RubyScript2Exe.

If you have a look at init.rb in rubyscript2exe.tar.gz [1], you
find an unused piece of code which tries to handle tk. Because
I don't know how to build TK applications, I'm not quiet sure
whether this works under all circumstances. At least, it used
to work with some of the demos... Is somebody able and willing
to test and correct this code?

> Good news is: wxRuby based application works great. Just one
> execuable, small enough size and runs perfectly fine. I will
> test few things under linux and will report them here.

WxRuby (on Windows) does native calls to the OS to show the
widgets. It doesn't depend on additional libraries. Although it
does depend on such libraries on Linux (e.g. Motif or GTK, (or
is it GDK?)), because there is no such thing as "native
widgets" on Linux...

RubyWebDialogs [2] is pure Ruby, so it works perfectly in
combination with RubyScript2Exe.

gegroet,
Erik V.

 [1]
http://www.erikveen.dds.nl/rubyscript2exe/download/rubyscript2exe.tar.gz
 [2] http://www.erikveen.dds.nl/rubywebdialogs/index.html