Many thanks for all this support. It has been a great help. Alex and I are both feeling better about this. I think from a legal perspective we have nothing to worry about now - but it's simply the sheer shock of realising that something like this was being done.
I have very mixed feelings about putting the "Creation" forum under subscribers. I do think it would be a shame if it was much less accessible to people just starting out.
There may be some other solution., though I'm not sure as yet what it could be.
Our problem is NOT a bootleg deck - if it was that I think the situation would be simpler. It is much more an "intellectual property" theft. Something that I, for one, was much less aware of as a potential problem.
Showing a deck in public doesn't necessarily make this more likely - though in my opinion it can make the issue much worse if someone can get hold of reasonable quality pictures to support their claims (by the way, it's one reason we really only show low-res pictures - they lose a lot visually and this has sometimes been very frustrating - but to show the "real thing" is just TOO crazily risky).
Our situation has absolutely nothing to do with AT - I doubt the person concerned even knows it exists. But I do dread a situation in which someone could come across work here and take some sort of similar action. That would be a real tragedy and to help to prevent this perhaps there does at least need to be some basic, thorough advice posted as a "sticky" in this forum - just to give people some guidelines on being careful.
It all sounds very legalistic but honestly, having had this experience I would now post things like links to good, free Non-Disclosure Agreements. We can explain clearly that none of us are lawyers (well, maybe some of us are?) but that we are simply compiling "best practice" based on our own good - and bad - experiences. I think that might go some way to protect people.
With my corporate identity background I at least moved very quickly on this and knew more or less what to do - and I think there may be no more problems once we get through this initial week of taking formal action. But a less experienced person might not know what to do and could get into real trouble.
As a community - which I think AT really is (I am more than ever feeling this after this experience - thank-you!) we do have some duty of care towards new members, even if we can only do something basic like an advice sheet.