You are correct that only the presentation of the gameplay, not the gameplay itself can be copyrighted. However CivProject is not in the all-clear area, as we did not replace everything, but added to it and made cumulative changes.
For example, we still uses the original illustrations on civcards and tokens and player mats, and the rulebook is just a heavily edited version of the original. However, as long as we don't make any profit, and provide our legal disclaimer (the one to the left), copyright is a non-issue by Swedish law (US law is another matter, but the site is hosted in Sweden nowadays). To actually sell copies you'd have to redo all components that isn't already original works however. That mean that I would need a few months to rewrite the rulebook from scratch, and someone would have to replace 132 drawings. And then I'd have to consult a lawyer to be on the safe side
And regarding the deep pockets, that won't work in Sweden. They might try, and they might hamper us by taking us to court, but in Sweden you can actually win a case without a budget, provided you are indeed right...
The worst thing they can do to me is file a lawsuit in the US, in which case I must hire a US layer to tell the court they don't have jurisdiction, or I'll lose by default...
Trademark issues, however, is another beast, as both Civilization and AH is registered trademarks I don't own, but I don't see how Take Two Interactive (owner of the Civilization trademark) can feel threatened by CivProject, and if Wizards of the Coast (owner of the AH trademark) threatens to suite I can live without a trade card back.
I made some further digging on the copyrights of the "originals".
1981 Civilization:
Published by Hartland Trefoil Ltd.
Copyright 1980 F. G. Tresham
1982 Civilization:
Published by The Avalon Hill Game Company
Copyright 1981 The Avalon Hill Game Company (Rulebook)
Copyright 1982 The Avalon Hill Game Company (Box)
"Made under license from Hartland Trefoil Ltd., Northampton, England"
1988 Civilization:
Published by H.P. Gibson & Sons Ltd., London
Copyright 1980, 1988 F. G. Tresham
"Made [...] under licence from Hartland Trefoil Ltd., Northampton, England"
1988 Civilization Wester Expansion Map:
Published by Hartland Trefoil Ltd
Copyright 1988 F. G. Tresham
1988 Civilization Wester Expansion Map:
Published by The Avalon Hill Game Company
Copyright 1988 F. G. Tresham
1991 Advanced Civilization:
Published by The Avalon Hill Game Company
Copyright 1991 The Avalon Hill Game Company
"Made under license from Hartland Trefoil Ltd., Northampton, England"
1998:
Avalon Hill disbanded
Hasbro, Inc. purchased "the rights to the Avalon Hill games and back inventory and the name 'Avalon Hill'"
Hasbro, Inc. transfers "Avalon Hill strategic board game line" to Wizards of the Coast, Inc.
1998:
Hartland Trefoil Ltd. bought by MicroProse Software, Inc.
MicroProse Software, Inc. bought by Hasbro, Inc.
MicroProse Software, Inc. merged into Hasbro Interactive, Inc.
2001:
Hasbro, Inc. long term licenses all Hasbro Interactive, Inc. rights to Infogrames, Inc., owned by Infogrames Entertainment SA
2003:
Infogrames, Inc. reorganized into Atari, Inc., still owned by Infogrames Entertainment SA
This information is based on printed copyright notices on the games, old press releases, company webpages, and Wikipedia (when no more reliable information is available to me). Based on this information the copyright is divided into two part.
The first part consists of the original Hartland Trefoil Civilization, the UK Gibson Civilization, and all versions of Civilization Wester Expansion Map.
This copyright is currently owned by F. G. Tresham, or Hasbro, Inc. If owned by Hasbro, Inc. it might be long term licensed by Atari, Inc. (making them the effective owner).
The second part of the copyright consists of the US Avalon Hill Civilization, as well as Advanced Civilization. It is currently owned by Hasbro, Inc. or Wizards of the Coast, Inc, depending on the legalities of their transfer.
An interesting note however is that Swedish law does not honor the American style default transfer of copyright from employees to the company they work for (though explicit contracts may transfer copyright to the company), so in Sweden the copyright might still be owned by F.G. Tresham, Mick Uhl, Charles Kibler, Dale Sheaffer, Bruce Harper, Jim Eliason, Jeff Groteboer, Eric Hunter, Steven Padgett, Gray Rapanos, Michael Roos, Jeniofer Schlickbernd, Jeff Suchard, and Charles Kibler. This is however mostly of interest if Hasbro, Wizzards of the Coast or Atari tries to sue me, in which case the case might be thrown out of court. This in addition to the fact that Swedish law currently (lobbying is in progress) only covers "damages", eg. lost sales, eg. nothing (at least, that is my layman interpretation) for non-commercial uses.