Hmm... that sort of information is very good to know. Thanks for getting this out there.
But that information does not match reality, at least in 2020. While the license had been stricer earlier on, you can of course do what you want with a MIDIbox that you own. SEQ v4+s have been sold on ebay, reverb.com and have and can be built and freely sold.
There had been problems with unlicensed commercial clones in the last decade, but it's something completely else if you do this on a small scale (10 units/year) or on a personal basi, e.g. building a second unit for a friend. See the license on midibox.org.
The whole "on the forums only" selling thing was an encouragement, not a requirement - to use the local midibox forums rather than anonymous ebay, so that the best level of support to users could be given.
Have a nice sunday and best regards,
Peter from midibox.org and midiphy.com