Sql ledger has the option to add a barcode to a part.
In 1.4, you will be able to add a barcode per make/model record.
How are barcodes added when using LedgerSMB?
Sort term solution:
It's not optimal for a UPC management but it solves the immediate problem:
Add a space separated list with the barcodes to the partnumber field
The partnumber is the "Number" filed on the same line as "Description" in the "Add Part" page.
And yes, "space separated list" works in the POS interface. (If you scan one of the codes in the space separated list )