Ewan....

This excerpt is from "A Treasury of Stephen Foster", Random House, 1946.

"Stephen Foster achieved a truly American expression. Born and bred in Pittsburgh, he was not influenced by the foreign music that enslaved the composers who lived in the more cosmopolitan seaboard cities. The voices Stephen heard were those of the minstrel shows, the singing and dancing of Negroes on the wharves of the Ohio River, and the sentimental songs of mid-century that were carried through the country by the "singing family" troupes, and were sung by demure young ladies who played the accompaniments on square pianos covered with brocade and lace."

Definitely supports your views that he wrote from the oral tradition. He would certainly have been exposed to the lines you mentioned above.

I'd say he was "original" as an arranger and publisher - no doubt, many of his songs are largely his own, but it's an interesting research question.

.....Tiger