Made an account just to post this:
I'm not a lawyer, but I've done alot of research personally on the topic of copyrights and intellectual property. As a kid I've despised them; they were a form of censorship that shattered my dream to make a free, non-profit Pokemon RTS game (which after a bit of inquiry on The Pokemon Company's stance on fanworks and IPs seems much more viable). Anyways, it motivated me to learn about them, to learn their weaknesses, and to fight them.
Copyright law is extremely archaic and outdated, and so there is a massive amount of grey area. What might seem like infringement might now be, and vice versa. Two things to know before we begin our discussion: first plagiarism and copyright infringement are two completely different problems (only the latter is illegal). You can make every effort to attribute the source with disclaimers, and it will help relatively little in court. Secondly, copyrights are different than trademarks; the former cover expressions while the latter cover terms and styles used to identify a company (so, if I were to make a fan-made Pokemon RTS I can't have Pokemon in the title- maybe Pocket Wars?). Apparently this is to avoid commercial confusion.
Anyways, let's begin our discussion.
First off, it's important to realize that as a website owner you have DMCA safe harbor as long as:
-If there is copyrighted material in anything you post or link on your site, that you
did not have actual knowledge and do not benefit from the activity and that you
immediately take it down when you learn that it is infringing.
-You register a DMCA agent to receive takedown notices (not sure if this is 100% necessary though).
-You explicitly tell your users about your policy for copyright infringement.
-You fully cooperate when you receive a DMCA claim on infringement.
As long as the owner of 3dsthemes.com follows these guidelines his website should be fine.
More info here:
http://www.dmlp.org/legal-guide/protecting-yourself-against-copyright-claims-based-user-content
Secondly, you can ignore that guy that said that a work can't infringe copyright because of "artistic expression"; in fact the nature of a work being artistic rather than educational actually goes against fair use (which, by the way, involves a four-factor test that is NOT LIMITED to the typical examples of parody, criticism, education, etc.). The good news is that this is actually the least important of the four factors (the nature of the copyrighted work). Most importantly is whether the supposedly infringing work had a significant negative impact on the owner's business.
More info on four-factor test here:
http://fairuse.stanford.edu/overview/fair-use/four-factors/
Thirdly (and this is from anecdotal evidence from several lawyers), the most important thing to know about this is that
most copyright-related cases never end up in court. Only the most egregous cases ever see a day in a courtroom, and usually one of the parties drops out after they've reached a settlement. It's less important to know how to win a court-case on copyright infringement moreso to never allow the problem to reach that stage in the first place (court cases are expensive and time-consuming for both parties, so most companies only use it as a last resort, and you should see it as such). Know which IPs you're mainly dealing which, know who owns them, and know how have they historically have responded to use of their intellectual property without their permission.
Game companies, compared to any other art industry, are the most lenient when it comes to use of their IPs, mainly because of the nature of how games work. While music only has the sound and books only has the narrative, video games combine all these different media to create an interactive experience unlike any other that can't be completely replicated easily. Aside from Square Enix and Disney (the two "copyright Nazis") most game companies not only tolerate fanworks, they welcome them. I remembered that Activision showed a fan-made movie for Call of Duty: Modern Warfare 3 in a promotion at E3. If this were the movie industry they would have lawsuits being stuffed into their rear ends!
Out of all the game companies, Nintendo is one of the most permissive in terms of their intellectual property. There are thousands of fanart, music remixes, and even entire games made by devoted fans that they allow without filing infringement notices. There were only two incidents I can name about them that might have some people worried. First is the incident in which Nintendo was supposedly taking down "Let's Play" videos on YouTube with footage from their game, though they were only taking away ad revenue from users that were monetizing their footage, and even reversed that policy, because "unlike other entertainment companies, [Nintendo] have chosen not to block people using our intellectual property
." Secondly is Project M, a Smash Bros-based mod that is considered "illegal activity" on MiiVerse, though that's mainly because it involved hacking the Wii to play it.
Bottom line, if you're dealing with Nintendo's content, chances are they're not going to go after you (they might even support you). Even if they do as long as you comply with their takedown notices you're in good shape. The only way you can possibly be in trouble by Nintendo is if:
A. Nintendo finds out what you are doing in the first place.
B. Nintendo actually objects to it (see above)
C. Nintendo files a DMCA takedown notice against said infringing content.
D. You don't comply with them immediately and take action to remove said infringing content.
E. Nintendo actually takes the time and money to sue one person running a amateur, low-budget website on something he loves.
F. You lose that court case (or "drop out" of it prematurely).
So, don't sweat it. Nintendo loves people making free, fanmade, creative stuff out of their stuff (although they do draw the line at piracy/profit). You might want to be careful with donations, though. Remember: Nintendo doesn't want to sue you, and you don't want to be sued by Nintendo. Make sure it doesn't happen, 'K?
Fun fact of the day: "Nintendo" means "Heaven of Duty"/"Heaven of Responsibility"!