A lot of people seem to post on this page trying to represent the views and goals of the project. So here's a clarification from the devs on the steam checks:
Redacted as a project has never been for pirates. We have had some simple checks in the past, not to prevent piracy but to mess with certain 'crack repackers'. This is simply because we despise that kids take the work of others and repack it with spyware, 'free installs' and requests for donations.
Activisions lawyers have complained about us offering a way for users without a legitimately purchased copy of the game to play online. As such we have decided to implement certain checks. The first is simple, if the client starts, it'll check for a valid subscription state in your local steam environment for the game as well as the dlcs.
The second check uses steam login system, oAuth. This is an optional check but users opting in will recieve VIP status and get prioritized in matchmaking, beta stuff, admin access to dedis and whatever we can think of. We may restrict certain features for non-oAuthed users.
In short, we have only so much we can do in terms of anti-piracy. We can however create a better product for legitimate users and hope that more users verify their purchase to gain access to it. We believe that the carrot is more effective than the stick and hope that Activision agrees.