[alanint]

There was really no organized and equipted Polish Army at the time of the Uprising. The Uprising was stagged mostly by civilians who had been equipted by the Allies and from captured weapons. There were certainly ex soldiers involved, who were released by the Germans after the surrender and were allowed to stay in Warsaw in some civilian capacity, (many were shipped off to work camps).
Based on the uniformity and completeness of the soldier's kit shown, I'm fairly certain this photo was taken at the time of the 1939 surrender and the Luger is an officer's private purchase, which was totally acceptable at that time.