gR - installation and computation

Hello everyone,
I would like to use R to compute some special hidden markov chain. I see that 
such those models are like dynamic bayesion network.
So, I find some doc about computation of those models in R, but I don't know 
how to install it on R and how to use it.
These doc talks about gR project.

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Alexandre DEPIRE
INRETS / GARIG