But that is the point, a sidechain is not its own network and therefore cannot be an "altcoin". Can a Bitcoin sidechain live without the Bitcoin blockchain?
I think not. because a side-chain is connected to bitcoin chain and is relying on it for its existence but at the same time it is disconnected in a way because you go on another chain and basically convert your bitcoins to new tokens on that chain....
at least that's how I understand it.
That is precisely what I have been debating with exstasie. A sidechain cannot be an "altcoin" because it is not in its own network. Although transactions of sidechain "tokens" are recorded in its own "database", it is still not an independent, and "alternative" network.