zulip
                                Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
                            
                        How to download and setup zulip
Open terminal and run command
                                            git clone https://github.com/zulip/zulip.git
                                        
                                        git clone is used to create a copy or clone of zulip repositories.
                                        You pass git clone a repository URL. it supports a few different network protocols and corresponding URL formats.
Also you may download zip file with zulip https://github.com/zulip/zulip/archive/master.zip
Or simply clone zulip with SSH
                                            [email protected]:zulip/zulip.git                                    
                                    If you have some problems with zulip
You may open issue on zulip support forum (system) here: https://github.com/zulip/zulip/issuesSimilar to zulip repositories
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