In CastPodder
File | Export feeds as OPML | podcasts.opml.
In gPodder
PodCasts | Preferences | Podcast directory |
file:///home/gdt/podcasts.opml
then
Podcasts | Channel list | Import from web
then tick all of the Subscribe boxes.
Even with the user interface bigosity for importing OPML in gPodder it's still pretty simple and beats typing a list of RSS URLs. With regard to OOXML, this is a neat illustration of the value to consumers of a single widely-used standard.
For those interested in the reasons for the move, gPodder has easy synchronisation with file-system style MP3 players.