This may be of interest to those who have not updated to OSX 10 Mavericks and above (there are some), for whom the updater doesn't work : it's possible to directly replace the source code. Download the latest version, extract the following plain text files :

get_iplayer
get_iplayer.cgi

Then replace older versions with these in the relevant folders (depends on your installation - search for it- for me, /opt/local/bin).

This gets me around the issue of updating to the latest version (v3.22 as of this post) without the need to update to a new Macintosh. This doesn't update the man page (get_iplayer.1) but that is a minor matter for most.