The NPC (ccp) tax is only for NPC customs offices. If your buddy joins a corp that has access to a 0% tax customs office then there will be no tax paid. But remember that the tax rates are set for each customs office, it's not like the normal corp tax. So he'd have to either convince them to set up customs offices at his planets or move his PI to the planets where they already have customs offices.

Salvaging, this was fun with the: Pi. Omg when a friend of mine came back from a mission (this time in RL) and he exported robotics he was crushed, but he thought it was a bug....for 600 pieces some 7 mil isk, ...then i told him to read about it...But in the end this is a good thing, taxation for Pi. Pi was getting out of control. he had 5 payed accounts, with 3 on each, doing Pi, and just at 30% for a 2k link(not more) / 2 day time, so he was lazy, he did not even bothered with the skill planetology...went strati for 6 planets lvl 5:) and boy it was worth it...a and best of all it was done in an empty system, nobody was there, all on the custom ofiice:) 25 k of it:) but again now i think he is f....or do you see any other solution.
Join a corp that has POCO....this POCO has let's say for instance if you are blue with them has 0% export tax..? no more tax...or the ccp still keeps tax. and then on top of the CCP tax, there is the corp tax?
Hope it was not boring...but man. in a hub 9 seraphims...omg is is on the table boys..if you can tank it:)