At this year’s GDC, Peter Vesterbacka and his flock of Angry Birds developers at Rovio held a panel on the breakout iPhone hit. But things turned a little awkward during the questions and answers session.

Someone from the audience asked Rovio what physics engine it used to make birds fly, wood splinter, blocks crash, and pigs die. The Finnish company openly admitted that it used the Box 2D physics engine. Our intrepid questioner then asked if Rovio would credit the software in game, to which Vesterbacka said “sure”.

And then, the audience member identified himself as Erin Catto, the creator of the open-source physics solution. Vesterbacka asked the plucky engineer to meet him after the panel. We assume it will be a friendly chat, and the Rovio staff won’t pelt him with tiny red birds.

Rovio isn’t obliged to compensate or credit Catto. MobileCrunch found the software’s license, which says “if you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.”

But, a “thank you” in the 50 million-downloaded game would be a nice shout-out to the original developer. Maybe we’ll see one in Angry Birds Rio or St Patrick’s Day.