There's a growing amount of free 3D models, as you may have noticed, and a recent addition is the Free Universal Construction Kit by The Free Art and Technology Lab (FAT). They are a "an organization dedicated to enriching the public domain through the research and development of creative technologies and media."
And in this case they certainly have.
The Free Universal Construction Kit is actually a library of eighty 3D STL-formatted models of connectors and pieces for ten very popular construction toys. You can use parts from the Free Universal Construction Kit with such toy kits as Lego, Duplo, Fischertechnik, Gears! Gears! Gears!, K’Nex, Krinkles (Bristle Blocks), Lincoln Logs, Tinkertoys, Zome, and Zoob. But wait, it gets much better: the parts are actually adapters that enable interconnection between different toy systems! You could start with K'Nex and join it to Lego parts, for example.
They offer three quite different ways to obtain the kit: download a fat ZIP file containing all eighty models directly from FAT; download individual 3D models from the Thingiverse repository; Download via BitTorrent from The Pirate Bay.
We have two thoughts on this. First, this creates a fantastic opportunity to build even more innovative designs, simply because each of the original toy kits has design advantages and disadvantages. If you have the Free Universal Construction Kit your new integrated design could leverage the strengths of one kit while avoiding the weaknesses of another within your specific application.
The second thought is perhaps a bit deeper. While the Free Universal Construction Kit is offered under a Creative Commons license, we're wondering how the manufacturers of said toy kits feel about this. In today's lawsuit-happy, protectionist corporate environment, could the manufacturers make a claim against this free kit since some of their intellectual property is partially used in each piece? Since the pieces are adapters and obviously are not produced by any of the manufacturers in the way they've been in the Free Universal Construction Kit we suspect not.
Evidently the relevant patents have expired on most of the kits - but two, Zoob and Zome still have active patents and thus those adapters are not included in the kit. They're just marked "Pending". Presumably when those patents expire, these adapters will appear in the kit:
The ZomeTool playset is actively protected by US Patent No. 6840699 (filed 1 November 2002, by Steven F. Rogers and Paul R. Hildebrandt). Models adapting to ZomeTool will be made available in November 2022