Arnaud Miege wrote:

I am relatively new and inexperienced with CVS, so apologies if this is trivial, but I couldn't figure out a way to do it.

I would like to be able to retrieve the files from that repository (note the release tag):

I followed the steps shown in the following wiki to access the files:

but couldn't find a way to specify the release tag,
Simply do like detailed in the section named Checking out the FlightGear source from the plib branch:

    In the "Branch or tag" section, select the "Choose branch or tag" radio button. Click the "Update list" button. From the "Branch or tag name" drop-down list, select PRE_OSG_PLIB_20061029. Click the OK button to begin the checkout.