It'll be open source, not sure under what license. Anyone will be free to steal it, use it, hack it whatever. There will also be an executable for ease of use.
1. The project started as a personal challenge. I'm not reading the source of vichan or tinychan I'm treating the boards as a blackbox and writing the code from the functionality I observe. I wanted to see if I could create an imageboard from scratch with a new language that would be useful for me in future projects.
2. C# has good performance
3. C# is easy to read so it'll allow newer programmers to reverse engineer the software and learn from it.
4. C# is hot in the market atm and I don't see it going away, making it valuable for people to learn about.