Forge started as a personal project and that's still what it is. The logic is solid — built on actual periodisation research and what I use every day. The UI has rough edges and there are things I haven't tested with anyone other than myself and a couple of mates.
If you want to use it, go ahead. Here's what I'd love to know:
iPhone: open in Safari → tap the share icon → Add to Home Screen
Android: open in Chrome → tap the three dots → Add to Home Screen
Worth doing — it's built as a PWA so it works better off the home screen than in a browser tab.