The tokens are frozen on the Ethereum blockchain at the end of the ICO, which means the genesis block (the first block that isn't built on another block) can be made with the balances on the Ethereum blockchain. The blockchain is then launched with this genesis block. The token holders in the genesis block must vote such that at least 15% of tokens (i.e. if I have 5% of all tokens, I am 1/3 of that required 15%) agree that this blockchain is a good blockchain before our tokens become transferable.
This can happen for multiple genesis blocks and thus multiple separate blockchains. It's unlikely that it'll happen for multiple chains, and near impossible for a blockchain with a false genesis block to gain enough network effect to out perform a correct genesis block.
https://www.reddit.com/r/eos/comments/71bvud/can_someone_eli5_this_statement/
Given that there's no limitation to the number of blockchains anyone can participate in, the chances for a continuous supply of new EOS blockchains are good. The possibility of being able to create an 'unlimited' number of blockchains is what a 15% holding gives you. You just basically say yes to any and all who want to use EOS.
Or will it be that token can only be transferred once?
If not, it's a possible eternal airdrop.