The best open source alternative to TeamViewer is UltraVNC, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to TeamViewer and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to TeamViewer are DWService (Free, Open Source), TightVNC (Free, Open Source), Remmina (Free, Open Source) and X2Go (Free, Open Source).
MultiVNC is an open-source VNC viewer that aims to be easy to use and fast. It includes the following features: - Bonjour/ZeroConf service discovery that automatically detects supported VNC servers in your network. - Virtual mouse button controls with haptic feedback.