Details about Blockstream sidechains and the effect on Bitcoin

Two authors (Adam Back, Greg Maxwell) of the Blockstream white paper on Bitcoin sidechains answered questions in a Reddit "Ask Me Anything" (AMA). Here are some answers from the AMA :

To implement sidechains in Bitcoin, it appears a "soft fork" may be necessary.

Sidechains (from Blockstream) are not treechains. The two are "orthogonal". Treechains could be implemented as a sidechain.

You can't readily transfer the non-Bitcoin asset to the bitcoin blockchain without a protocol similar to "colored coins".

Blockstream aims to have "open development" with code available at https://github.com/blockstream.

Blockstream seems to employ two (or three) of Bitcoin's seven current committers. These Blockstream-employed committers do not see this as a problem due to employment contract items and the overall consensual nature of Bitcoin.

Ethereum can be made to work with as a sidechain to Bitcoin.

An altcoin may ship with an early sidechain implementation before Bitcoin has a chance to have a community debate and (maybe) do a soft fork to enable sidechains.