Awesome tool but what is the legality of this? Where is it sourcing the episodes from?
It's a client, none of the copyrighted work is stored in the software, it merely facilitates the user to load it in a media player.
> Where is it sourcing the episodes from?
The answer is in the source: https://github.com/trakBan/spongebob-cli/blob/eac7eded094a48...
TLDR: seems to be fetched from a source called "megacartoons".
See http://www.law.cornell.edu/supct/html/04-480.ZO.html
(Eg torrent sites are also illegal in many countries despite merely linking to copyrighted materials)
The main reason for the post is that your original post which implied that just because it didn't host the copyrighted content itself made it OK from a legal perspective - this is probably untrue.
One similar ruling for the ECJ is below, which again demonstrates that this would likely be illegal in Croatia:
https://www.wipo.int/wipo_magazine/en/2016/06/article_0007.h...
As a further note, not only is the application itself probably illegal to develop / release, it is almost certainly illegal to use. It's unlikely to be the subject of enforcement action though for the users (Although I would be surprised if Viacom was cool with this).