Alternativas ao SlideMail para Ruby com licença comercial

• Ruby
  Todas as plataformas Windows Mac Linux Chrome OS Android iPhone Apple Watch Android Wear iPad Android Tablet Windows S Web Self-Hosted BSD Haiku PortableApps.com Slack F-Droid Chrome Ruby Gmail Cloudron Amazon Echo (Alexa Voice Service) PureOS (Purism)
• Licença comercial
  Qualquer licença Licença gratuita Licença Open Source Licença comercial