Following are few open source SCADA softwares:
1. Free Scada
Supported OS: Windows
License: Freeware
Free SCADA provides for end-users flexible tools for visualization and interactive control of any industrial process.
2. IndigoSCADA
Supported OS: Windows, Linux
License: GPL
A small footprint SCADA system entirely developed in C and C++ with multiple OS support and multiple front end protocol drivers.
3. openDAX
Supported OS: Linux
License: GPL
OpenDAX is an open source, modular, data acquisition and control system.
4. openSCADA
Supported OS: Windows, Linux
License: GPL
openSCADA is an open source Supervisory Control And Data Acquisition System. It is platform independent and based on a modern system design that provides security and flexibility at the same time.
5. S.E.E.R. 2
Supported OS: Linux
License: GPL
S.E.E.R. 2 is a full featured SCADA / Historian / Aggregate Analysis System developed to work as a ‘front end’ for mod_openopc.
6. SCADA ProcessViewer
Supported OS: Windows
License: GPL
Crossplatform SCADA written in Free Pascal language
7. ScadaBR
Supported OS: Windows
License: GPL
ScadaBR is a SCADA (Supervisory Control and Data Acquisition) system with applications in Process Control and Automation, being developed and distributed using the open source model
8. Szarp
Supported OS: Windows, Linux
License: GPL
SZARP is a full-featured, open source SCADA system for Linux. Client programs are available for Linux and Windows.
You may compare the features of these in detail and decide which is the best suitable for you.