Interesting, which part of it? The fact it consumes from subscene.com without asking them or because downloading subtitles are illegal?

Reason why I'm asking is because I don't know, and obviously I don't feel like getting in trouble for a weekend hobby project.

In a way there is nothing illegal about offering links to another site. But subtitles are a derivative work of the original text so they are copyrighted and also you typically only need subtitles for movies obtained in a questionable way. So you immediately get involved in legally shady stuff.

The main problem is that if you get sued you stand to lose a lot of money, even if you eventually win.

Nothing illegal about this application.