This is a sticky post and will be updated regularly.
Information Systems
- Name: Obsidian
- Intention: Wikipedia-style, mark-down information system
- FOSS: no (freeware)
- OS: Linux, Windows, MacOS, Android, iOS
- Name: BookStack
- Intention: Documentation-style information system
- FOSS: yes
- OS: Self-hosted
- Name: Zettlr
- Intention: Wikipedia-style, mark-down information system
- FOSS: yes
- OS: Linux, Windows, MacOS
Memorisation Systems
- Name: Anki
- Intention: Spaced repetition system flashcards
- FOSS: open-source, free
- OS: Linux, Windows, MacOS, Android, iOS
Office Applications
- Name: Libre Office Suite
- Intention: Writer, presentations, spreadsheets, etc.
- FOSS: yes
- OS: Linux, Windows, MacOS
- Name: TeXstudio
- Intention: LaTeX editor
- FOSS: yes
- OS: Linux, Windows, MacOS
Miscellaneous
- Name: Minder
- Intention: Mindmap creation tool
- FOSS: yes
- OS: Linux
- Name: Forest
- Intention: Study timer and distraction removal tool
- FOSS: no (paid application)
- OS: Android, iOS, add-on
- Name: GoodTime
- Intention: Study timer
- FOSS: yes
- OS: Android (available on F-Droid)
Yeah, it’s completely free and can even be user without internet.
If you want to host your content on their servers though (for a website or sync), that costs money.
Foss stands for free open source software but the free refers to libre, not gratis, not the price.
Since obsidian is not even open source (vs closed source) I don’t think it can be free (libre). And even if it would be open source, it doesn’t mean that it is libre. It could also have a weird or no license. Gpl v3 is a good example of a libre license.