Hey there! Creator of Kontxt.io here, which was listed on the site. Quick correction.

- It's actually free. - Still under development. - It has a CMS and social network to organize, share, and discover with others. - Anyone can add the annotative collaboration features directly to their own site with a single line of code to boost engagement and sharing to grow their audience.

New feature: Stylize your highlights and add a promotion to every share. Perfect for fundraisers and charitable donations.

Example: https://www.kontxt.io/document/d/QNebKRiN9ghcqTb1U8StSZJEwlT...

Description: I highlighted a site. Put highlights on their own page. Added a background. And added a clickable promotion (to donate to the Red Cross) with analytics to see views and clicks.