I'm not sure (literally not sure!) if the Postdam Declaration meets the spirit of the Franck Report and Szilard Petition. One aspect is this:

If such public announcement gave assurance to the Japanese that they could look forward to a life devoted to peaceful pursuit in their homeland and if Japan still refused to surrender, our nation might then, in certain circumstances, find itself forced to resort to the use of atomic bombs.

One the one hand, the Potsdam Declaration asks for unconditional surrender. But I don't think that's disqualifying on its own and it also includes passages like this, which I think you could reasonably argue do meet the criteria laid out above:

the Japanese military forces, after being completely disarmed, shall be permitted to return to their homes with the opportunity to lead peaceful and productive lives

Japan shall be permitted to maintain such industries as will sustain her economy and permit the exaction of just reparations in kind, but not those which would enable her to rearm for war. To this end, access to, as distinguished from control of, raw materials shall be permitted. Eventual Japanese participation in world trade relations shall be permitted.

But there's another part of both the Franck report and the Szilard Petition: They were concerned that once nuclear weapons were used, it was inevitable that other nations would develop them, e.g. this part:

If after the war a situation is allowed to develop in the world which permits rival powers to be in uncontrolled possession of these new means of destruction, the cities of the United States as well as the cities of other nations will be in continuous danger of sudden annihilation.

Though I suppose they only urge that Truman to consider these issues, and maybe he did.