Etherscan has an option for linking the source [1], in which case they compile it and verify the result against the bytecode that's publicly available.

Edit: the source itself is based off of [2]. The custom part is ```contract PonziCoin...```. It's well written in the way that all Solidity code is well written...

[1] https://etherscan.io/verifyContract

[2] https://github.com/humaniq/ico-contract/