Alternativas ao Shtuff Chat para Software as a Service (SaaS) com licença gratuita

• Software as a Service (SaaS)
  Todas as plataformas Windows Mac Linux Chrome OS Android iPhone Apple Watch iPad Android Tablet Web Self-Hosted Software as a Service (SaaS) Telegram Ruby on Rails
• Licença gratuita
  Qualquer licença Licença gratuita Licença Open Source Licença comercial