Hi Warren, great!
We are currently working on a better/easier integration of custom frontcalls into GST.
For the standard mobile scanbarcode frontcall it seems we simply need to switch to the apple frameworks in vnext (you may try other barcodes/QR-codes with the little app , its not limited to PDF417) and remove the zbar lib from the core (which saves final executable size). We need however to make sure that no decoder previously possible disappears in this transition, so there might be issues.
Regards, Leo