Hi! The app is fully open source - you can compile and install it yourself if you’d like. Hard to get more free than that!
We do not distribute binaries outside of iOS appstore and Google play because we’re a small team and we cannot commit to providing customer support to users who do not use those platforms. It’s hard enough supporting those already! On our website (scroll to bottom of Get your new Pebble smartwatch here ) we mention explicitly that we only support iPhone and Android.