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)
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.