I'm very glad that my project interested you!
I've made this change based on the fact that Simon has Julius & HTK only as a runtime dependency.
So there is no sense just to disable to user ability to use Julius&HTK backend. So by now you can freely build & run Simon without Julius&HTK. But if user want to use Julius&HTK backend instead of Sphinx, Simon will tell to user that he have to install Julius & HTK manually. And if user will do it he will be able to use Julius & HTK backend also.
Good luck! I look forward to feedback and wishes for Sphinx backend.
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Best regards,
Vladislav Sitalo