Instead of flashy rhetoric you should concentrate on the fact that competing implementations is healthy; but the ones that threaten to break protocol are dangerous. That's what sold me.
Competing implementations of Bitcoin, such as Litecoin and Primecoin, are called altcoins because they establish their own independent alternative socioeconomic consensuses/majorities.
Hostile implementations of Bitcoin, such as XT and Classic, are declarations of war because they attempt to threaten Bitcoin's existing consensus-critical distributed ledger.
But there are other implementations, like libbitcoin I believe, that aren't altcoins, and are net positives for the
Bitcoin ecosystem. Isn't that right?
It gets confusing and idiomatic (esp for non-native speakers) if we have to distinguish between the friendly positive-sum competition of btcd vs the cutthroat zero-sum competition of GavinCoin.
I'd classify other implementations like libbitcoin and bctd as
complementary, not competing, in that they all share the same goal of maintaining the One True Holy Ledger.
But let's defer to the core dev, if gmax has a better suggestion for the taxonomy/nomenclature.