There were several functional alpha clients even before the crowdsale. PoS vs PoW is somewhat beside the point anyway, as the codebase is still using SHA3 PoW:

There were several functional alpha clients even before the crowdsale. PoS vs PoW is somewhat beside the point anyway, as the codebase is still using SHA3 PoW: http://github.com/ethereum http://github.com/ethereum