They're breaching copyright law, they're just not being punished as they're such small fry. And limited run key caps would probably be okay too, but there's always a risk that one may be made an example of. It's a risk I'd not be willing to make for just a few grand.
If you get written permission from the copyright holder, then all is well.
It's a funny thing copyright law, for example, if I sell you a painting, then I transfer with the sale my copyright over to you and you can make as many reproductions as you like; if I sell you a sculpture, then I retain the copyright and if you make a copy, then you're breaching copyright... Very easy to trip up, it's so convoluted.