In the future, please provide scans of the cards in questions; however, since this is a simple question, here you go.
http://pokebeach.com/scans/plasma-blast/92-g-booster.jpg
http://pokebeach.com/scans/black-and-white/71-zoroark.jpg
http://pokebeach.com/scans/plasma-blast/11-genesect-ex.jpg
It is similar to Mew EX (which is found in our FAQs):
Q: If there is a Mew EX and a G Booster/Scope in play, would Mew be able to use that attack, or would only the Genesect EX be able to use it?
A: No. Mew EX can only copy the attacks printed on a card, not ones given to a card by a tool, TM, or other effect.
Genesect EX does not "Have" G Booster as one of its attacks to copy. Genesect EX is only able to "Use" the attack printed on the tool card. There in lies the difference.
Carpey said:
Hello, I've been playing around with a deck that revolves around Zoroark BW. Zoroark's attack, Foul Play, reads: "Choose 1 of the Defending Pokemon's attacks and use it as this attack." I'd like to know if this attack can use the G Booster attack on a Defending GenesectEX that has it equipped.
