I am still quite the newbie but if open source software is so great, why aren't GIMP and the AMD drivers kicking ass compared to their proprietary counterparts?
I use Inkscape, Gimp, MyPaint, Krita, and Blender professionally. I used to use Illustrator/Photoshop/Maya/etc, but those don't run on Linux (well), so I embraced the Open-Source alternatives and guess what? In a lot of ways, for what I do, they work better. Don't get me wrong, they have their rough edges, and they don't have near as much industry support, so you'll always be able to find fancy plugins for the standards, etc.
The reason no one wants to use them is they have to fight an uphill battle, and just haven't won on every front yet. Adobe & Autodesk pay for the spot-light position. No one is dumping millions of dollars into getting the OpenSource tools into schools, and internet ad campaigns, etc. But, just like Linux, they can't be stopped, and will continue gaining features and support support until the commercial competitors are dumping millions into their products for only a few unique features. At that point, it simply isn't profitable trying to compete, and new development (even commercial) will be put into expanding the "open standard" tools.
Much of the example work on my resume (http://reign-studios.com/philipwitte/) is made using open-source tools on Linux (Arch, GnomeShell).
Also, a few things I've made with open tools which aren't on my resume:
The fair thing would be a try before you buy model, not with a demo, but the WHOLE GAME for 24 hours. The FULL version. Let the client appraise the quality of game and make his choice if he wants to support you or not. Let him judge if the price you ask is fair or not.
Steam does this all the time. They haven't had a free weekend for Linux title yet, but I'd say it's only a matter of time till we see one.
As for the pirates... Idiots that deserve to get their box pwnt.
If you want to pirate a game pirate a Windows only title. As has been stated many times 90% of the Linux titles have or still are available DRM free either from their developer's sites or where part of a HIB.
Sure I pirate music all the time as well, but I actually go see most bands in concert which makes them far more then buying the album anyways and if their music is available through a site like Bandcamp I buy it in FLAC.