I guess it could be a wing that has been won in a comp, bought on ebay etc. (similar to the T2T ones - where the company sponsors taken off them?). It might not have been an advertising stunt. Personally, I had a look around on google and based simply on the logo and palm name (there was no web address) it would have been a poor advertising attempt.
However, if he didn't have clearance to fly and was at a dodgy altitude - the only advertising it gives is bad - for us! Although reading various glasto blogs the crowds seem to have been in favour of the pilot and where cheering him on...this of course only until he stalled, fell onto the tent roof, slid down and diced a few people in the crowd up... (that bit didn't happen obviously...)
Surely somebody knows who flys that wing - it's pretty unique?!?
Out of interest, it's amazing how many members of the public refer to the paramotor as either a light aircraft, paraglider, microlight etc. etc.