Sounds like that was meant to weld the verts that were split to keep the edges hard.  Was a P4 thing.  I don't think P6 cares about that.

Anim8or is free.  Make a cube (double-click to set the parameters - leave divisions at 1).  Go to Build--Convert to mesh.  Then Build--Convert to subdivided.  Now convert back to mesh, and save as OBJ through the Objects menu.  Should have nicely rounded edges.

John