After much deliberation, I made the decision to open source Packstack's codebase. I was initially hesitant to do this because it makes it much easier for other developers to spawn copycat projects. The upside, however, is that developers have been contributing code that makes the core product better.
My plan is to maintain the open-source codebase and continue developing requested features. While I do this, I'll also be developing a native app for Packstack.
The app will be available on iOS and Android, though I haven't determined if it will be a freemium model with in-app upgrades or a flat price. In the meantime, Packstack.io will help me build up a following that I'll be able to leverage once I release the app.