diff --git a/README.md b/README.md
index 57e3bc65..f54db170 100644
--- a/README.md
+++ b/README.md
@@ -227,6 +227,7 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
   * [Jitsi Video Bridge](https://jitsi.org/Projects/JitsiVideobridge) - WebRTC compatible Selective Forwarding Unit (SFU) that allows for multiuser video communication. `Apache` `Java`
   * [Kandan](http://getkandan.com/) – Kandan is an Open Source Alternative to HipChat. - `AGPL`
   * [Let's Chat](https://sdelements.github.io/lets-chat/) - A persistent messaging application that runs on Node.js and MongoDB. `MIT` `Nodejs`
+  * [Mattermost](http://mattermost.org/) - Open-source, on-prem Slack-alternative. It can be integrated with [Gitlab](https://about.gitlab.com/). ([Source code](https://github.com/mattermost/platform)) `AGPLv3/Apache 2.0` `Go`
   * [Mumble](http://wiki.mumble.info/wiki/Main_Page) - low-latency, high quality voice/text chat software `BSD` `C++`
   * [Node-Chat](https://github.com/IgorAntun/node-chat) - A not-so-basic open-source chat with admin features. - `MIT` `Nodejs`
   * [RetroShare](http://retroshare.org) - Secured and decentralized communication system. Offers decentralized chat, forums, messaging, file transfer. ([Source code](https://github.com/RetroShare/RetroShare)) `GPLv2` `С++`
@@ -778,6 +779,7 @@ See also [Documentation Generators](#documentation-generators), [Wikimatrix](htt
  * Non-[Free](https://en.wikipedia.org/wiki/Free_software) software must be marked `⊘ Proprietary` next to the title, and added to [non-free.md](non-free.md)
  * Software with no development activity for 6-12 months may be removed from the list.
  * The syntax for links is ``[Name](http://homepage/) - Short description ([Demo](http://url.to/demo), [Source code](http://url.of/source/code)) `License` `Language` ``
+ * License and programming language should be written as AGPLv3/Apache 2.0 Go/Javascript
  * Please limit the short description of the project to **250 characters**.
  * The list of contributors can be updated with `git shortlog -sne`