I've split the project in two parts, PicoTorrent and PicoTorrentCore. PicoTorrentCore is cross-platform and builds on GCC4.8.
The linux directory contains build scripts to build on Linux, which is used for the TravisCI builds.
And there's no UI yet, right? If you plan to write one, I'd suggest Qt, since you use C++ extensively already.
I hear qt is excellent, but would encourage you to do distinct ui code for each platform, in that platform's native ui libs. You'll look like a fish out of water otherwise.
To be clear, Qt is as native as you can get on X11 and Wayland. There is no vendor-controlled UI toolkit as on Windows or OS X or Android or ...
Yeah, that's what I'm planning in order to keep it small and tidy.
You might want to start with a web UI then (like SyncThing). This provides you with a simple way to display your data and you get Mac / Linux / etc support for "Free" while also allowing your Windows users to have simple network access.