As Lego (the old blocks not the 'new' hi-teck stuff) are now in the public domain, can I make a game where the graphics are made out of lego blocks?
Well, I can, but is it legal?
First, I am not a lawyer, this is not legal advice, if you follow my advice and get sued and lose your house then it's your fault not mine.
Unfortunately, as simple as that question is, it really needs to be broken down into two questions.
1) If I get sued for copyright infringement, will I win?
Maybe! Assuming those pieces are in fact public domain now, then it seems like a rather clear victory. Now, for the sake of this entry, I'm going to assume you win, unquestionably. I don't know that for certain, but we're just going to make that assumption.
2) Will I get sued?
Unless you have a nice big legal war chest to rely on, getting sued is almost as bad as losing. You can't hope to match Lego's legal funds. It will not happen. You'll go to court, and you'll probably blow thousands of dollars just on prep work. And then, even if you win, there's no way you're getting that money back without a second court case - more money, and you're not even guaranteed to win that one.
You may want to read this story. For posterity, here's the important bits:
So, when you say "Well, I can, but is it legal?", that's really the wrong question to ask. The right question is whether or not Lego will permit you to do so, and whether you have the money to defend yourself if Lego decides they won't let you do so.
I'll let you decide, for yourself, how likely Lego is to object.
Again, not a lawyer, not legal advice, get a lawyer.
(Disclaimer: segments of this were copied from a similar reply I made to a similar question.)
This kind of questions are usually answered by lawyers after a good amount of money, and not even them will tell you for sure. To be sure you'll have to meet a judge in a courtroom, which I guess is what you're trying to avoid :)
If Lego is actually public domain you'll probably have no problems as long as you don't use the Lego trademark/logo or anything else that isn't public domain.
Just because the basic LEGO patent has expired, that doesn't mean that all their other intellectual property is in the public domain, nor that the laws are the same everywhere you want to market your own product. If your game represents itself as being in any way remotely related to LEGO toys, the LEGO company or trademarks, you could face trouble.
If in doubt, come up with your own slant on the construction idea, or pay for proper legal advice.