Fix sentence

added comma

README.md

@@ -175,7 +175,7 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
 
 ### Custom
 
-  * [Actor](https://actor.im/) - Actor is a fast open source messaging platform with rich mobile and web clients. ([Demo](https://app.actor.im), [Source Code](https://github.com/actorapp/actor-platform)) `AGPLv3` `Scala`
+  * [Actor](https://actor.im/) - Actor is a fast, open source messaging platform with rich mobile and web clients. ([Demo](https://app.actor.im), [Source Code](https://github.com/actorapp/actor-platform)) `AGPLv3` `Scala`
   * [Cherry](https://github.com/rafael-santiago/cherry) - A tiny webchat server. `GPLv2` `Go`
   * [Freenet](https://freenetproject.org/index.html) - Anonymously share files, browse and publish "freesites" (web sites accessible only through Freenet) and chat on forums. ([Source Code](https://github.com/freenet/fred)) `GPLv2` `Java`
   * [Friends](http://moose-team.github.io/friends/) - P2P chat powered by the web. ([Source Code](https://github.com/moose-team/friends)) `MIT` `Nodejs`