I just tried synching to the Ethereum Classic blockchain with geth --oppose-dao-fork. I was using Ubutntu PPAs but I hit an error at a certain (can't find which one now) which was a known issue with that version of geth.
I compiled geth from source and am now using version 1.6.7-unstable-dfd07624.
Now when I try to continue synching the chain, I get
flag provided but not defined: -oppose-dao-fork
How do use Ethereum Classic with the latest geth?
I think this flag has now been removed. (I can't find it in the source code, but neither can I find the commit that removed it... It's definitely not there though.)
I imagine the two forks - ETH and ETC - have now diverged to the point that supporting both versions in one codebase would be a burden to the ETH developers.
Ethereum Classic has had its own homepage, GitHub repository, and official releases for a while now. You should be able to find what you need there.
