DEX is also for those who want to explore the ps3 and run their own code on it using the tools leaked with the SDK. on CEX the code must be signed by you-know-who. on DEX it can run also (it seems to be only...) if fake signed (easily done with the tools provided with the SDK).
if their ps3 was less or equal 3.55 when they bought it, they should downgrade to 3.55 (with progskeet or e3 flasher) and then they can do all they need. no solution yet for those with FW greater than 3.55 out of the factory.