Yes you can webchat is open source: github.com/net-bitsDotNet But you would need to modify the flash/js parsers as this protocol is based on IRCX but it is different protocol ircWx (IRC Web Extension). But you can give it a try maybe most of it will work.
Another thing, you need support for flash xml socket on the irc server, and socket policy issued at connection to the irc or need to run separate flash policy file server.
All clients connecting with flash sockets needs flash policy file. I've never used lightirc so I don't know what it is exactly doing, but we have built general purpose flash policy file server that we use for flash socket connections.
That is one thing good about flash sockets because they allow separate flash policy server on the same ip. On the other hand, for websockets, irc server needs internal implementation for websocket handshake.