commercial distribution

[Mike Cu]

Hi,
I have a question on what is considered 'commercial distribution'.
I guess if you sell then it makes it commercial but if you don't sell but use advertisment in relation to it does it make it commercial ?
Like, add advertisement/third party software into the installer ? i.e the installer bundles for example the 'Yahoo toolbar' and the application. Before installing the actual application, the installer asks the user if he optionally
 wants to install the 'Yahoo toolbar' and then continue with installing the actuall application,
or what many popular downloading sites do : present adverts when clicking on an link for downloading it,
or add adverts to the web page that you can download the application from

I am looking after the artistic license 1, which says  : 

aggregation of this Package with a commercial distribution is always
permitted provided that the use of this Package is embedded; that is,
when no overt attempt is made to make this Package's interfaces visible
to the end user of the commercial distribution. 

What is an "interface" ? and what is "when no overt attempt is made to make this Package's interfaces visible" ?
thank you
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