I unpacked the zip file and ran the 106KB exe and pow had a local web server running that appears robust, comes with a number of sample scripts and has a decent API and documentation. I ran the amortization example, showing monthly payments for my house loan over 25 years. That page took 2,736,400 cpu clock cycles to generate on my PC where 3 million = 1 ms. That's very quick! Reading the source code I notice that it uses Ajax to do the call to the C script.
For those that are skeptical about using C code in a web server, G-Wan implements dynamic buffers with a library of calls to load files from disk, do text manipulation, even find and replace strings. "Standard" scripting code such as PHP requires functions like url_encode, escape_html to deal with html or escape values. In G-Wan these functions are provided, as is high precision CPU time so you can measure how long it took to output a page to the CPU Cycle! Overall I get the feeling that it has been very well thought as a powerful yet light weight web-server.
I have one suggestion that could enhance G-Wan. Make it work with SQLite as it appears a natural fit.