AntennaPod is open source and pretty good if you're on Android. Podcast Addict isn't open source (I don't think) and it's not as pretty but it'll be the most powerful podcast app you ever use.
Pocketcasts is definitely a better overall app experience, however, that still didn't stop me from switching to AntennaPod well over a year ago. It's a solid app and one of the best FOSS app projects around.
No regrets. I just wish I could manually sort podcasts on the subscription page.
Man, I wonder why nobody has forked this already? It seems like a really easy way to get a new podcast app up and running. PocketCasts is widely loved, it's just the business practices and lack of features that have put people off.