....The timeline doesn't seem to make sense - he returned to England at the end of the war, but was also living in South Africa until around late 1903/early 1904. Perhaps he had returned to South Africa between those two times?
....Any record of his having been with the Boers?
…."At an inquest yesterday on Samuel C. Osborne, aged 50, servant to Mr. Pierpont Morgan, who cut his throat on Wednesday night, it was stated that Osborne had good health until five years ago, when he was living in South Africa. On the outbreak of the Boer War, the gentleman to whom he was acting as valet and butler came to England, leaving Osborne in charge of his property. The Boers came and turned Osborne out, and he was forced to join their ranks. He waited on the sick and wounded at Spion Kop and Ladysmith. His health became shattered, and at the end of the war he returned to England in straitened circumstances. The jury returned a verdict of "Suicide." "
….His full name was Samuel Claydon Osborne, and he was born at Mildenhall, Suffolk, in 1858. His death was on Wednesday, 3rd February 1909, in the St George Hanover Square, London, registration district.
….Pierpont Morgan is better known as J. P. Morgan, the American financier and banker.
Evening Express, Tuesday 9th February 1909
