I have an old copy of 3DX back when it was free, and I still use it. But you'd have to read the EULA to see if it specifies an expiration date for it. CrazyBump, for instance, was free in Beta but explicitly said that the free license would expire as soon as the pay version came out.
It's an interesting discussion, though, and I think it should stay open. Warez threads don't get deleted unless someone is specifically asking for a download site for commercial software, or someone is posting links to same. Since you don't want Deep Exploration but the old, free 3D Exploration it's fair game IMO.