i airdrop to all holders of the bitshares asset "FREE" my own asset "xyz"?
that is technically possible .. a asset is the same as BTS on the blockchain .. BTS has ID:0 while other assets have higher IDs ..
so you can airdrop on bitUSD, bitEUR, bitCNY ....
currently there are no scripts/api calls to directly access these data from the client .. but a script can be written to parse the blocks and figure it out