Bookmark Tree - Web annotations is described as 'extension allows you annotate you bookmarks: leave comments, mark text or even create links on other web sites. Also it allows you to share your bookmarks with other users' and is an app in the Web Browsers category. There are more than 25 alternatives to Bookmark Tree - Web annotations for a variety of platforms, including Windows, Online / Web-based, Android, iPhone and iPad. The best alternative is Joplin, which is both free and Open Source. Other great apps like Bookmark Tree - Web annotations are Standard Notes (Freemium, Open Source), Evernote (Freemium), CherryTree (Free, Open Source) and Markup-Annotation Expert (Free).
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.
Markup is an expert on web and document annotations. It allows you to highlight everything on PDFs, web pages, and ePub books. With Markup, you can easily add, manage, and back up your markups in one place.
Colorful & powerful sticky notes app for Windows & Phones. Set reminder alarms, attach them to any website or document, organize them using folders/tags, sync sticky notes between devices & send notes across LAN or to any contact across the globe.
NixNote, formerly Nevernote, is an open source client for Evernote . It is written in Java so it will also run on Windows & OS-X, but the primary focus has been to try and get a usable environment for Linux.