http://runningwithscissors.com/?p=2318

I wish they would update the postal games here. I don't know what this means for postal here will we get it free or will it be removed.

1) There's already a thread about it, but it may have gotten buried a bit.
2) It doesn't mean anything about the game on GOG. Only thing being open sourced is the code, not the assets. So even if you do compile the code, you will still need all the assets to play. Similar to how Jagged Alliance 2 is open source, yet still sold all over the place.