The fact that it's a LGPLv3 licensed library gives me pause to use even in our backend infrastructure (never ever in code running on client devices). The v3 situation is so complicated that even fsf had to come up with a matrix to explain how their own licenses play with each other. Not a very comforting situation:
First, as complicated as the licensing interactions around the GPL may be, the quite simple fact is that the (L)GPL's requirements only apply if you distribute code, so there is no more reason to take pause when using an LGPLv3 library in backend infrastructure than there would be if you were using a BSD-licensed library.
As for client devices, it is possible to distribute proprietary applications linked with LGPL libraries, though there are requirements you must follow. The amount of time it takes to figure out and comply with those requirements is minimal compared to the person-hours that went into developing ZeroMQ, which you are getting for free.
Edit: apparently ZeroMQ includes a static linking exception to the LGPL, so you don't even have to comply with the LGPL's most onerous restriction when linking with ZeroMQ! http://zeromq.org/area:licensing
Well it's FUD in the sense that I really, actually feel Fear Uncertainty and Doubt about using any code under GPLv3 license. There's good reason to [https://www.google.com/search?q=gplv3+for+commercial+use&oq=... ] worry. Large companies I've worked in before this (with teams of technically savvy lawyers on staff) have been known to promulgate an outright ban of such open source software in their production stack.
Now, nothing makes me happier than being proven wrong in this case (especially with the static linking exception AND this little nugget "It is the intention of the ZeroMQ community to move gradually towards the Mozilla Public License v2, as a replacement for the current LGPLv3 + static link exception" ).
So in a sense, my comment here has had a positive result not just for me but also for anyone else reading this thread and worried about the license. So on balance, I'd credit this subthread more for clearing up of FUD than the reverse ;-)
When Blizzard made Starcraft 2, I am sure they were very concerned by all the many software licenses out there, but then decided to use every tool available to make the game better, released at a earlier date, and have resources directed elsewhere than reinventing LGPLv3 licensed libraries.
The gaming industry is however a very competitive one, where every choice is critical. A company there could not survive if they took unnecessary costs. Yours might be different, so maybe the competition won't eat your lunch while you are busy reinventing wheels. Do a risk analysis and decide how much money and time it is worth, and ask yourself what happens if a competitor happens to be in the exact same spot and decided to instead go with the free alternative.
http://gplv3.fsf.org/dd3-faq