Actually, I believe it is. Part of the EULA is to not modify the executables.
Don't like it? Don't post here. No one's forcing you to come here.
We have rules here, and there's a reason for those rules. And partly because of those rules we (CFC) have a good relationship with Firaxis, Breakaway, and Atari. Not too sure about 2k, but it wouldn't surprise me.
All of the other fan sites I've been to have simular rules. So it's not just us.
I'm quite familiar with the site you linked to. And yes, it does have a lot of illegal files there. Again, there is no such thing as abandonware. It's a fiction. Either the game's creators still hold the copyright and therefore it's piracy, or they have released it to PD and you can freely download it. But to call it abandonware is not accurate.
And plenty of people still play the older civ games. They've tried the newer games, and don't like them.