Ethereum isn't an altcoin; it's a platform.
Ethereum is an altcoin. Just because it is a platform as well, doesn't mean its not an altcoin.
Mastercoin is a platform too, but its still an altcoin at the end of the day.
Saying Ethereum isn't an altcoin is misleading.
I don't think it's an altcoin. I mean, it's debatable. I'm not trying to mislead anyone. But when Ethereum gets compared to dogecoin, then you have to say something to make the distinction. Ethereum is more of a distributed computing system that uses a token called ether for its operations. Ether plays many roles in the system. It's not just a coin; it's also fuel for contracts. How would you make the distinction. (And I think Masteroin is a metacoin, not an altcoin.)