We have made other scriptable applications using primitive scripting languages that we've created, but I think using a mature, existing scripting language provides a lot more flexibility.
Mozilla's SpiderMonkey documentation seems to be slightly out of date, so I had to modify Mozilla's sample Hello World code a bit to get it to compile and run, but I eventually got there. I think it's pretty cool to be able to have a compiled app be able to load and execute code from a scripted language.
Mozilla SpiderMonkey 17 (implementing SpiderMonkey 1.8.5) is available for download here:
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