Kozeluch was born near Prague, which, in the context of the era, makes him a Bohemian rather than a Czech. He belongs to that throng of musicians that filled late 18th-Century Vienna, and which included Dittersdorf, Vanhal, Salieri, Clementi, Schenck, Hoffmeister, von Winter (based mainly in Münich but many operas performed in Vienna), Mozart, Krommer and the two Wranicky/Vranicky half-brothers Paul/Pavel and Anton/Antonin, to limit myself to those of roughly the same generation (all born between 1739 and 1761). Kozeluch’s dates make him indeed Haydn’s younger by 15 years and Mozart’s elder by 9. Among all those, he was one of the most sought-after composers of his time: Archbishop Colloredo of Salzburg even offered him the post he had just kicked Mozart out of, and for a more-than-doubled stipend – and Kozeluch was highly regarded enough in Vienna that he was able to decline. Now of course poor Kozeluch is but a neglected nam vying for some crumps of light n in the gigantic shadow cast by Haydn, Mozart and Beethoven.
I haven’t heard a lot of Kozeluch, but what I have is of great quality and certainly warrants listening to more: three Piano Trios on cpo and 4 symphonies, performed by Concerto Köln on Teldec.