We're running a nonprofit online conversation service, Lyra. It's a space for online conversation which respects language and attention, provides powerful tools to control audiences and news feeds, and doesn't take investment or ad revenue. We're already sustainable!
Hello! We are actually in the process of being accredited as a not-for-profit organisation. It's a bit more difficult than incorporating a PLC, so it will take a bit of time :)
The points which are most blindingly marvellous are a) control over your audiences and your news feed and b) a respect for language and words, which comes across in lots of different places in the interface.
Hello! Lyra also supports 1 to 1 conversations (private conversations with just one person in the audience). These are just the same as private messages.
Lyra also supports panel discussions (public read, but only a few people are allowed to comment) and blogging (private read AND private write).
www.hellolyra.com