In reply to Tomas M..

As noted in my comment below, it might be GPL'd, but that doesn't say you have to distribute it. All it means is that whoever has access to the software must be given access to the source. For PHP software, that's almost always automatically the case.

In this case, Arc is an internal product used at WaPo and owned by them. They're under no obligation to distribute the software or source to anyone else.

(If they had a self-installable copy they licensed out, ala GitHub Enterprise, they would have to include the source; they could still choose to charge for those copies though.)