Taskpad is described as 'An open source Taskpaper clone written in C#, using WPF' and is an app in the Office & Productivity category. There are five alternatives to Taskpad for a variety of platforms, including Online / Web-based, iPhone, iPad, SaaS and Mac. The best alternative is TaskPaper. It's not free, so if you're looking for a free alternative, you could try taskpaper+. Other great apps like Taskpad are TodoPaper (Paid), TaskOnPaper (Paid) and TaskOPad (Paid).
Make lists and get organized. TaskPaper is a plain text to-do list that’s surprisingly adept. Outliners are powerful, but hard to use. Text editors are easy, but without structure. TaskPaper feels like a text editor, but has the power of an outliner.
taskpaper+ is a portable browser-based todo program (i.e. it runs in a web browser; however it doesnt need an internet connection--it has its own local webserver). Under the skin your precious task lists are saved in plain text files written in a clear, logical way.
TodoPaper is a simple, lightweight, and easy to use to-do list application for Windows. TodoPaper records your to-dos with the flexibility to make your to-do list as simple or as detailed as you desire.