Terms of ether sale:

https://www.ethereum.org/pdfs/TermsAndConditionsOfTheEthereumGenesisSale.pdf

clause 19.9

Risk that Ethereum Platform May Never be Completed or Released.

Purchaser understands, that while Ethereum Team will make reasonable efforts to complete the Ethereum
software, it is possible that an official completed version of the Ethereum Platform may not be released
and there may never be an operational Ethereum Platform.