Not exactly, before introducing artworks from KOEI into this mod, we thought copyright might be a problem. So we checked the Japanese copyright law (http://en.wikipedia.org/wiki/Japanese_copyright_law) to make sure that we are not infringing someones copyright. We found that non-profit reproduction of artwork is in the exception list, as it stated: Non-profit performance: Works can be performed or exhibited freely if the performer is not remunerated, and the audience is not charged an admission fee. And as it required that If one of the above exceptions to reproduce a work publicly is used, the person reproducing the work must cite its source We clearly stated the source of leaderhead art and give full credits to KOEI.
Since we are not lawyer, our action was based upon the resource of Japanese law we could find. If the wiki is wrong or you know some other Japanese laws forbid what we do, please tell me, and well use other pictures instead. Thanks.
It's good that you've tried to consult the Japanese law. I don't know about copies sold in China, but the copies sold in the UK come with a license agreement that says the users are not allowed to make any copy of the program, including artworks, other than for backup. The user would have to have agreed to this license terms before they can install the program. Did you not have to agree to such terms to install your copy of Koei's ROTK?