Althoug a lot of the popular attention is directed toward buffer overflows and use-after-free errors, that does not mean that C programs are free from the same business logic vulnerabilities as programs written in other languages, or even that those errors are less frequent; Just that buffer overflows are easier to detect.

The other language that I would put next on the priority list is Java, which gecko also seems to not support. I guess gecko is more web-oriented, which makes sense for a security tool, I suppose.

Anyway, wish you lots of successes!