How to make the website such as wpmudev.org what is behind?

How to make website such as wpmudev.org and which themes did you use? Which plugins?
Is it possible to have chats in the way you organize it with chat plugin you offer? Are the plugins offered the same one used with the spmudev.org.

I have to admit that sometimes I experience slow load that is not necessary on user side ... Is the problem for that complexity of scripts?