MemoMaster is described as 'free outliner software to create, administer and reference texts and calculations in the familiar tree structure. It enables intuitive searching, browsing, and organization of information' and is a Note-taking Tool in the Office & Productivity category. There are more than 100 alternatives to MemoMaster for a variety of platforms, including Windows, Mac, Android, Linux and iPhone. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Microsoft OneNote. Other great apps like MemoMaster are Evernote (Freemium), CherryTree (Free, Open Source), NoteLedge (Freemium) and Zim (Free, Open Source).
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, can be copied, tagged and modified either from the applications directly or from your own text editor.