Lago Billing - Open-source alternative to Stripe Billing and Chargebee
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Metronome - Metronome helps software companies launch, iterate, and scale their usage-based business models, with billing infrastructure that works at any size and stage.
Standard Notes - A safe place for your notes, thoughts, and life's work
Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.