The fact that Dillo is programmed in C makes it portable to other operating systems. Shouldn't Windows be your principal target, considering that the "democratization of Internet" would have more impact because of the larger userbase of this OS?

Definitely NOT. 
Let's go by parts: the fact that Dillo is programmed in C is not a guarantee of portability. In fact, library dependence is much more important. 
If the libraries are portable, or have equivalent APIs, is relatively straightforward to make a version for the supporting platform. If the function libraries do not exist in the target platform, porting becomes a titanic task. 
On to the other part, the endeavour of democratizing the access to Internet is very much tied to these 
two facts: 

Dillo keeps the hardware requirements low and constant. 
You don't need to pay software licenses to use Free Software. 

Micro$oft (windoze) is the exact opposite, and even more, it artificially raises the hardware requirements. If someone uses that platform, he will have to renew his computer periodically (to do the same things he was doing before), and also pay a new license every time there's an "upgrade". 
If, on the other hand, a Free Software platform such as GNU/Linux (with dillo) is opted for, an old or new computer can be used for as long as the hardware lasts, without fearing that it will stop working. And, of course, there is no need to pay a license fee. 
The second option allows people who are without an Internet connection because of its "high costs" to enjoy the advantages of the information era. 
It is true that there's a need to educate and inform that: 
It is FALSE that you need to renew your computer every three years. 
It is FALSE that you need an ultra modern computer to connect to the Internet. 
It is FALSE that you can't have good internet access with a phone line. 

Those myths (when taken as true) are only the basis of a multi-million dollar business that exploits those who believe them!