This is going off topic a bit, but I've heard "licensing restrictions" around this before, and I'm rather hazy on *which* licensing restrictions people are talking about. From a code perspective linuxcnc-ethercat is GPL v2 and the Ethercat library we use is LGPL-2.1. LinuxCNC itself is GPL v2 (or at least that's what Github thinks), so the code itself should be clear. There aren't any CLAs in place for any of this, so there's probably a chance that someone, somewhere, could claim ownership of some of it for historical reasons, but that's true of almost anything and not a big risk IMO.
@sittner made a comment about EtherCAT itself not being open-source, but IIRC that's not really a thing that should matter here, although of course you'd want your lawyer to sign off on that. I doubt more than a tiny handful of the hardware that LinuxCNC supports is open source anyway, or has explicit licensing allowing our use. Anyway, I'd expect that using the EtherCAT spec to implement devices would (a) be fine (at least in the US) given
en.wikipedia.org/wiki/Google_LLC_v._Oracle_America,_Inc
. and (b) it'd sell more EtherCAT hardware.
In the medium term, though, it's a lot easier to maintain EtherCAT code outside of the LinuxCNC tree anyway.