Websockets? HTML5 Websockets will always limit your throughput to the point that maxlength configuration doesn't mean much (just test with 1M messages). All browsers have their own internal limitations and idiosyncrasies, in my experience.

I'm not sure I understand your comment. If you're speaking about Zurl limits, the max-size option has no effect on WebSockets since of course the session could go on forever.

So, this is the level where GPL actually becomes a problem (for me anyway). I can see how it is still reasonable for zmq itself of course.

Hmm, how is the GPL a problem? Are you considering modifying the project and need to keep it closed?

If you put GPL code into your code, your code becomes GPL regardless of whether you modify the original GPL code.

Indeed. However, Zurl is a standalone server process, not a library that you link with.

I know that the GPL's effects across process boundaries can be a bit of a gray area depending on how coupled the processes are, but as the author I'll just clarify that it's safe to use Zurl's ZeroMQ-based interface ("ZHTTP") without the result counting as a combined work. The fact that I've published ZHTTP as an independent spec may help ease minds on this: http://rfc.zeromq.org/spec:33

Ah, I see what you've done here - makes sense. It's nice work too.