I notice the Arc source is littered with a few references to Scheme 48, specifically things not working in it. But if that got fixed, then you'd have access to C libraries, because IIRC Scheme 48 was built to interface well with C.
The only thing that seems to affect, going by comments, is the conversion from characters to integers and vice versa. If that's the only actual problem, there are only about ten places in the Arc code that need some replacement fix.
