The mechanism of accumulating randomness in the beacon chain is inspired by the RANDAO, there is no DAO that is used to obtain randomness seeds. The detailed explanation of how does it work in the beacon chain is here. The power of each validator with respect to the randao computation is significantly limited on the beacon chain.
Security Considerations section of the EIP states that the randomness output that is exposed by the RANDOM opcode becomes known to network participants when the parent block gets published, application developers MUST take this into consideration. In that regard the new opcode doesn’t differ much from the DIFFICULTY as block.difficulty is known to the miner of the block in advance and should there be an incentive the difficulty value could easily be shared or even sold.