IP confusion
3D products produced on an industrial scale automatically attract "unregistered design right" in the UK, rather than copyright. This is like copyright in that you have to prove copying for there to be infringement, but its duration is much shorter (10 years from "first marketing" of an article made to the design). However parts of designs that must fit or must match another part are not covered. Parts of a design where there is some design freedom are covered.
Broadly this means that an aftermarket for spare parts is legitimate, provided that the aftermarket manufacturer copies only those parts of a product they have to for the part to fit the original. This can be very complicated to assess, as one of the leading cases in this area, involving parts for Dyson vacuum cleaners, shows:
http://www.bailii.org/ew/cases/EWHC/Ch/2004/2981.html
You can also pay a fee to register your design. If you do you can get longer cover and don't need to prove copying. But registered designs don't cover hidden parts of complex products, parts fitting other parts, or parts whose appearance is solely dictated by function, again leaving the door open for aftermarket companies to operate if they are careful.
If you patent aspects of products, like the Magsafe connector on Macbooks, then the aftermarket needs a licence to reproduce that. This is why savvy OEMs will try and patent these kinds of features.
As for Lego - the basic connection was patented in the late 50s, so has long expired, and any other rights in the basic blocks have expired. I believe Lego may have tried to get a 3D trade mark registration for the block and failed. However the word Lego is a registered trade mark.
This means that a third party could make a brick that is the same as the bricks that date back to the 50s. Stamping Lego into it would be TM infringement (upper/lower case would make no difference). They could say their brick fitted Lego bricks provided they made it clear that it was not an original Lego brick.
The UK-IPO (Patent Office as was) explains the difference between these various types of protection here: http://www.ipo.gov.uk/types.htm
phew.
PS don't take this as legal advice... it's late
Biting the hand that feeds IT
