People:
In the short term, this compromise is a good thing, yes, but it still caves in to these backwards, wrongheaded censors!
This is not a win at all. The game could still have to be changed, and we don't know the extent of these changes yet. Do not celebrate until the game is released.
Now, the win conditions are:
1. L4D2 comes out completely unmolested.
2. L4D2 does not come out at all because there is no compromise that can be reached, which results in the debate being opened up (remember, Michael Atkinson has banned discussion of an 18+ rating for games - you can't even talk about getting it implemented!). This results in Atkinson being widely recognised as full of shit from outside the gamer community, and his status repealed. This will likely have the same effect as 1. - an 18+ rating implemented or more games available under 15+ (less ideal).
Sort of win:
3. L4D2 is edited slightly. Australia still gets its game, and its gameplay is untouched.
4. L4D2 is castrated by the changes, and large amounts of gamers simply import or install mods which turn the game back into its intended, ultraviolent version.
Fail:
5. L4D2 is castrated and people lamely accept it - there is no real effort to mod or import to get around the censor. Or, doing so is illegal or impossible.
6. L4D2 is cancelled for Australia.
Epic fail:
7. L4D2 is cancelled for Australia, and Atkinson succeeds in turning it into fuel for the moral panic he is swept up in which ensures that the country becomes even more strict in its censorship.
8. L4D2 gets through in Australia being castrated, and Atkinson sees this as vindication and evidence that game devs will tone down the violence if he demands it. With obvious consequences.
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It could still be any of these paths. Don't celebrate until you see what happens.