Yes, it can have same codes for 2 products even its identical or different but question is what is the good practice to save others time.
We should not use the same Barcode for any different item even its the variation of the same item like size or colour, As most of the stores use this as unique identifier and inventory will be tracked correctly and also there might be price difference for items as per size and colour. so it can not be use as unique.
We can only use for same item as many times as you want it will remain same.
So solution is never use same Barcode number for different items and use the cheaper Website like Codesforamazon.com for Unique Barcodes.