closed source is fair if you have the rights to the code - and it is your code ... if not - i do request that you release the code to the public if it contains any open source material in it ... and yes - that is a formal request ...
The service uses some open source software (starting from the operating system), but not every open source license is viral like GPLv3…
apart from that your project looks very promising AND if it is available for more than just files - we can look at incorporating it into the granite ecosystem ...
As a seller is already able to authorize payment generation on his behalf, it is easy to imagine the service being extended to support also arbitrary payments. This is a feature that is being considered and it may be implemented in the future.
ill keep an eye on the project anyway - but the closed source scenario means we are at your whim of development ...
unless of course you are willing to make changes on a private contracted level ... then thats a different story
...
If some community is willing to pay for a coin being included, then it can be considered. For example,
in 2014 Coinkite announced an altcoin inclusion contest in which the final decision was made based on the amount paid. (Currently their
altcoins roadmap page states that their integration charges start at $25 000).