What are some alternatives?
When comparing Vikunja and Microsoft To-Do, you can also consider the following products
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Wekan - The open-source Trello-like kanban (built with Meteor)
Zenkit - Zenkit is the home you always wanted for your ideas, your projects, your business.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
WeDo - WeDo is the best platform for planning and daily tasks management activities.
Google Tasks - to-do list app that integrates with Gmail and Google Calendar