Josef Kuderna worked in various professions – as a civil engineer, actor and professional gymnast with the Deutscher Turnerbund (German Gymnastics League) in Langenzersdorf. In 1910 he was sentenced to eight months' imprisonment for selling printed matter stolen from the Vienna University Library to various bookshops. Two years later he was sentenced to five months' imprisonment for selling forged Wagner silhouettes in Bayreuth. In November 1918 Kuderna, who also collected pictures, mainly drawings, opened an antiques and painting business at Reisnerstraße 16 in Vienna's 3rd district. It was registered in the name of his wife Aurelia, née Mayer, and was initially highly successful. In 1925 the art dealer Ferdinand Spany brought charges against Kuderna for fraud, defamation and blackmail in connection with the sale of an alleged Rubens painting from the Liechtenstein collection but failed to obtain a conviction. In the 1920s, the business suffered, and although Kuderna moved to a site in the city centre, Wallnerstraße 6a, his Old Masters Gallery was finally forced to close in 1931. In 1931/1932 he was convicted yet again of misappropriation of artworks on consignment. In a further case in 1932 the Vienna Landgericht (provincial court) and Oberlandesgericht (higher provincial court) sentenced him to a further fifteen months' imprisonment for forgery and swindling the heirs of Ella Wendel in New York. In 1936 Kuderna sold forged silhouettes to Viktor Schützenhofer, director of the Technisches Museum Wien, for which he was imprisoned for eight days that year.
Following his illegal membership of the SA in 1937/38 and his subsequent employment as a civil engineer in Heeresbauamt II (army building authority), Kuderna attempted again in 1939 to work as an art dealer. With the support of Julius Fargel, he made several applications for pardon so as to obtain a character reference from the Gauleiter’s office in Vienna that made no mention of his criminal record. Although all of his petitions were rejected, he was employed briefly in 1940/41 at the Hermann Göring-Werke in Linz and then as a building inspector for the Vienna city council. In 1941 the Lehmann Vienna address directory was already listing him as retired. In 1944, as a private individual rather than the owner, he offered Gottfried Reimer a portrait of a woman by Ferdinand Georg, an "old family heirloom", for the "Sonderauftrag Linz". Reimer refrained from buying it and a painting by Eugène Delacroix, also a "owned by the family".
After Aurelia Kuderna died in 1946, the business in her name was deleted from the register of companies. Shortly afterwards, Kuderna sold forty-five watercolours by prominent Biedermeier artists, including a number of works by Josef Höger. They had been looted in early 1945 from the Prince of Liechtenstein at Fürstengasse 1 in the 9th district, as indicated by the insignia "F. L." on them. They had been acquired from the Vienna art dealers Artaria & Co./Gilbert Schiviz, Karl Löscher, Gilhofer, and Universitätsbuchhandlung R. Lechner/Walter Krieg. During a house search in Kundera's apartment in 1947, rustic kitchenware and plates stolen from the art dealer Theodor Sebesta were secured. The Landesgericht für Strafsachen (provincial court for criminal matters) in Vienna sentenced Kuderna to eight months' imprisonment in 1948. He was exempted from serving the sentence on health grounds. During the protracted trial, Kuderna stated that he had given valuable drawings from his collection to public institutions such as the Albertina, the present-day Wien Museum, the Theatermuseum and the Heeresgeschichtliches Museum (HGM) (Museum of Military History). With the exception of the HGM, this statement has been verified, although his collector's stamp has been found to date only in the Albertina. Between 1944 and 1950, in particular, he gave these institutions bundles of drawings and photographs but also sold large quantities in order to earn a living. Thus, in 1948/49 three oil sketches by Hans Canon and Hugo Charlemont were acquired and are still held by the Österreichische Galerie. Their provenance has not been determined to date.