Symbiont would technically take custodianship of the BTC in such an arrangement?
None of that has anything to do with Symbiont (and all of this transpired before Symbiont even existed). In this case, when I say "us", I was talking about "us" as the Counterparty co-founders.
This is really interesting. So according to your research or the advice you received, simply programming an autonomous and decentralized mechanism such as this makes the programmer a custodian of the funds or at least liable for what happens to them?
That's the thing: such a system is not really "decentralized". The bitcoin would have been essentially held with a 3rd party until the trade completed. Multisig, etc. might be able to be employed, but if you want to remove the need for the user on the BTC side of the trade to "be there" to complete it, then someone else would have to do it for them. This service would just sit on top of the decentralized exchange protocol built into Counterparty, and take the BTC side of the trade for the user offering BTC, removing the responsibility of them having to sticking around to complete the trade.
Which 3rd party would have held the BTC? Counterparty can not be made to escrow the funds autonomously?
_Someone_ would need to handle the BTC, _only_ in this specific case. Note that this is _only_ the case with BTC, and _only_ if you don't want to place _any_ burden on the user that has the BTC to stick around after they place the order. Basically, Counterparty doesn't have the same degree over escrowing BTC that it does with native assets, for purely technical reasons which have been explained elsewhere.
Have you guys mentioned this to Erik V at Shapeshift?
Not that I recall. You're welcome to, though.
I sent him a msg in skype.
btw who owns that counterwallet website?