What is source code? GPL

What is source code?
Stupid question, right?
Wikipedia defines source code as any collection of computer instructions (possibly with comments) written using some human-readable computer language, usually as text.

But what is your definition of source code, the GPL license requires changes, and developments to GPL licensed code to be openly shared under the license.

So can I demand Wikipedia provides my with there specific implementation of 'LocalSettings.php' file which contains their database connection string the lines:

$wgDBserver = "mysql.wikipedia.org";
$wgDBuser = "root";
$wgDBpassword = "password";

are all source code right? So why is Wikipedia not in violation of the GPL license by not providing them to me, and what other exemptions can be made?

Thanks