Open source? Metaexchange should check this out :)

In case you are not aware.  You can use bUSD anywhere bitcoin is accepted via shapeshifts Firefox and Chrome browser pluggins

https://shapeshift.io/tools.html#lens

Merchants can also offer checkout via bUSD, BTS and many other alt coins and receive bitcoin seamlessly with the shifty checkout button.  I'm not sure if the merchant is able to designate which coin they prefer to receive or if its just bitcoin.

https://shapeshift.io/tools.html#shifty

Both of these tools are open source.
Keep in mind that there is a spread involved so it will end up costing you more for this convenience.