What are some alternatives?
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.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Standard Notes - A safe place for your notes, thoughts, and life's work
BibDesk - BibDesk is an organizational software created to help you edit and manage your bibliography. It keeps track of your bibliographic information as well as said information's associated web links and files. Read more about BibDesk.
CherryTree - cherrytree – giuspen
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.