I'm fairly experienced in FRED2 Open, and have other programming experience (2 years of C, 4 years of Java, another 4 years of PHP, and I can't count how many I've done web design with CSS and HTML).
Yeah, that's all fantastic.
Why is there no SCP avatar under your nickname, and why aren't you slaving away at the Open code?
Someone better change this for Great Justice.
To be honest, the code base is a bit intimidating if you're coming at it for the first time.
This is probably going to start a flame war, but I reckon the documentation could use a bit of effort - it's hard to find exactly what you're looking for, and you really need to have an idea of the whole codebase in order to do anything - e.g. the scripting can affect the HUD - I didn't know this when I first started looking at it, and I'm still not entirely sure how it affects the HUD

There are also some things that aren't really documented at all. Feel free to flame away folks.