OP is different for everyone, and really as an arbitrary concept is fairly ridiculous. For example, a definitive statement 'that mod is OP' is completely ludicrous without having something to compare it to. It's only when you start getting into mod interaction that you start getting into OP.
For example, let's use one from a while back... "Equivalent Exchange 2 is OP!". As a statement by itself, this is fairly meaningless because there is nothing to compare it to. However, the statement "EE2 is ruining the balance in x mod pack, it is totally OP there!" might well have merit, because now you have a declared 'balance' of power for it to be in excess of. It is at least a point which CAN be debated. The former cannot, because we have no clue where the litmus test of power level lies.
Remember: For something to be 'over powered', it needs to be compared to an average power level.
As far as the previous discussion on copyright... I prefer to think of it in terms of politeness rather than legality. Legality aside, if a mod author doesn't want you distributing it without his permission, it is just plain rude to then do so. Forget about suing, forget about 'legal action', forget about EULA's and all that jazz. If the creator of something has asked that you ask to use it, then it is rude to just jack it.
Some people use GNU, open sourced, or otherwise 'free to use, free to distribute' disclaimers. For those, it's cool, they've actively told you they're fine with it.
Some people want to reserve their distribution rights. Why they want to doesn't really matter. There are some legitimate reasons, there are some less than legitimate reasons, but that's really aside from the point I'm trying to make here. They made it, they should be able to make a polite request.
Maybe they're wanting to keep track of download numbers to see how popular it is. Perhaps they don't want their mod in a mod pack with another mod that either directly conflicts with it or has some other unintentional synergy or whatever. Perhaps they are just plain greedy and want the adf.ly revenue (all five bucks of it). Regardless of the reason, to my mind, it doesn't matter. If they say 'get permission before redistributing', and you don't, that puts the egg on your face, and any rationalizations are completely irrelevant. Don't like it? Don't use the mod in your mod pack. Or, tell people 'hey, if you really like this mod, I've included a config file in the download, but you're going to have to download it and drop it into the mods folder yourself. Or use the ATLauncher that pretty much does that for you (it'll bring up the download website or adf.ly link for the mod to download manually). But distributing a mod after the author asks you not to? Party foul. Uncool.
Just my two cents.
