I ended up choosing the GPL / LGPL for hardware, too. I asked this question on some other sites and the following answer was spot on:
I spent quite a bit of time looking into this, and there is not really
a useful solution. For some general background try
In a nutshell, GPL (and all other software licenses) rely on software
being something that can be subject to copyright. In general hardware
can not be copyrighted, because copyright is only granted to creative
or artistic works, but with some weird exceptions like software, IC
masks, yacht designs (!). "Useful articles or utility works" are not
generally subject to copyright, but some powerful industrial lobbies
got some concessions, as otherwise a software "work" would not be
protected under IP laws, although specific software algorithms can be
So anyhoo, software is an oddity in copyright laws, but "copyleft"
licenses can turn copyright law to its advantage. There is no such
ability with hardware. The only way to protect a hardware design is to
embody a patentable idea that the design relies on. "Data files" for
engineering use are not software, and are not "creative" (in terms of
the law), so it is unlikely they have any form of protection. That
doesn't stop many companies attempting to claim copyright on data, the
threat of legal action even if unfounded in law is often enough to
scare people off.
Legally, you can use copyright to protect your drawings, but you can't
protect the actual circuit, nor the PCB layout, and therefore you
can't insist on share-alike clauses to be followed. What we are left
with is a "social contract", i.e. a statement that a design is shared
for general use but please be nice and share your modifications.
There are some OSHW specific licenses, such as CERN, OSHWA, OHANDA,
these have the same drawback as GPL, copyright gives little protection
to hardware designs. But they can be a nice way to stamp your project
as being in the OSHW spirit.
tldr; use GPL or LGPL, CC-BY-SA, MIT, etc as you like, as a statement
of intent, but realise they have little legal teeth. Other OSHW
oriented licenses are equally ineffective to protect or control the
use of electronic or hardware designs.
The above answer was posted to https://forum.kicad.info/t/using-the-l-gpl-as-an-open-source-hardware-license/1925/2
Some other useful articles on the subject: