Why is it more profitable than mining with 0% pool?
If they pay more than mine themselves that mean they have losses every time they borrow your rig, isn't it?
However, what 0% pool are you referring to?
If you mean Eligius, then no that isn't a 0% pool.
Yes they charge no fee, but no you don't get 100% PPS.
Their payout system has an upper limit of 100% PPS (but of course you can never get more than that)
However, their long term luck shows that you should expect below 100%
Firstly, orphans will mean that the long term average is expected to be below 100%
Secondly, their pool itself means that it will also average under 100% due to their slow block change.
Thirdly, their payout system is advantageous for miner who block withhold - and that also reduces the long term average.
The worst case for block withhold is a PPS pool - where the withholder loses no payout, however it is the pool that loses BTC, not the other miners.
Eligius payout system means a block withholder can lose less BTC, when block withholding, than mining at a PPLNS pool. It is the other miners that pay for it, not the pool operator, so the pool operator has no incentive to use another payout system, like PPLNS, that favours a block withholder less.