New Post: What does the lack of multithreading mean?

There's alot of talking about the lack of multithreading in R. I'm a long time R-programmer (under Linux) and I'm trying to up my game by involving the general C# devlopers at my office. However, I can't really understand what the lack of multithreading actually means. If I develop a standard webb-application that use R-enhanced data via R.NET, for my 12 clients, how will they notice that R is not multithreded? Can only one of them use the app at the time? Will the app be slow?

/TIA