Symbian is not yet open source software. It is going to be.
Whether it isn't or is has nothing to do with signing or not signing. That's a separate thing/policy.
You can self-sign any application yourself, if the application is not using any capabilities (privileges) where self-signing is not enough.
You can also use the Open Signed Online method for free signing:
For more details read this:
"Signing is the process of encoding a tamper-proof digital certificate into an application. The
certificate identifies the application’s origin, and grants access to those Capability-protected
APIs in Symbian OS that the application declared at build-time.
"On Symbian OS, protected APIs are those that allow sensitive operations, such as those that
• access end users’ private data, thus potentially breaching privacy
• potentially create billable events, thus costing the end user money
• access the mobile phone network, potentially affecting its operation
• access handset functions that can affect the normal behavior of the phone
• potentially impact the performance of other applications running on the phone.
"Developers creating straightforward applications should find it possible to avoid the signing
process altogether by not using Capability-protected APIs. Alternatively, where certain
Capabilities are required, the developer may rely on the user to grant blanket permission to
the application at install time, or ‘single shot’ permission at run time (for example, agreeing to
send a message) if the security policy of the Device Manufacturer allows it. Although this is
possible on some devices at the time of writing, there is no guarantee that Device
Manufacturers or network operators will always allow unsigned applications to install on their