R's capaability of dealing with multiple requests

Hi,

I am interested in integrating R with a Java front end. Before deciding to 
use R I am concerned about multi-threading.

I have been investigating R's capability of dealing with multiple requests 
simultaneously (multi-threading)
and have looked at Luke Tierney's 2001 notes for ideas for future releases 
of R at http://www.stat.uiowa.edu/~luke/R/thrgui/thrgui.pdf

Is a single instance of R capable of dealing with multiple requests 
simultanouesly or does a new instance of R have to be created for each 
request?

Regards,

Dr. Simon Pears