I think what alfa1 is saying is that
forum policy explicitly states that posted maps become public domain. This is a perfectly fine policy; copyright in this case is considered to be voluntarily ceded by the copyright holder, in countries where public domain legally exists. Since Two Tanks was posted on the fora, Two Tanks is now public domain.
However, this policy was formally stated after stive was AFAICT last seen on the fora, and (despite the retroactive application to the forum policy), I think it's probable stive hasn't seen it (and any legally required grace period for removal has surely lapsed). Artists typically want widespread enjoyment of their works (particularly if initially released for free), so it's likely stive would
want Two Tanks to be public domain. Nevertheless, I don't think it would be particularly
nice to
assume this to be true and act on it, without his explicit assent (he hasn't responded to a PM, so it's doubtful we'll ever get such; too bad).
Consequently, I haven't publicly mirrored Two Tanks. Despite the fact that it is public domain, I have decided to only use it for experimentation, since this is the only thing we can currently be sure stive wanted.