It seems like the Barcode module is hardcoded to handle nodes instead of other types of modules. Since fields can be attached to many different entities(users,terms, etc) the module could be changed to handle other entities.
I found this issue because a user filed an issue Entityforms when trying to use Barcode with an Entityform.with my module
It seems the only function that assumes entities are nodes is _barcode_sanitize.
I will attach a patch....