ReSIProcate
http://www.resiprocate.org/
The ReSIProcate project consists of a stack and a collection of applications. The ReSIProcate stack is currently used in several commercial products and is considered very stable. ReSIProcate is ideally suited to individuals or companies that are implementing one of the following SIP applications.
SIP SIMPLE Client SDK
http://sipsimpleclient.com/
Description: SIP SIMPLE client SDK is a Software Development Kit for easy development of SIP multimedia end-points with features beyond VoIP like Session based Instant Messaging, File Transfers, Desktop Sharing and Presence. Other media types can be easily added by using an extensible high-level API
OpenSourceSIP
http://www.opensourcesip.org:8080/clearspacex/index.jspa
Twisted
http://twistedmatrix.com/trac/
Python SIP Stack
PJSIp
Open Source SIP Stack
Vovida
http://www.vovida.org/
MobiCents
Descriptions: Mobicents is an Open Source VoIP Platform. It is the First and Only Open Source Certified implementation of JAIN SLEE 1.0 (JSLEE, JSR 22, JSR 240). The Open Source SLEE and SIP Server.
download at sourceforge.net
WeSIP
WeSIP is a SIP and HTTP Converged Application Server built on top of OpenSER!!!
WeSIP adds a J2EE layer to OpenSER so you can benefit from the existing OpenSER modules and features, which already implement nice functionality like registrar,nat traversal, diameter authentication or radius accounting at blazing speeds,while at the same time enjoying the ability to develop and deploy new converged SIP and HTTP applications in an J2EE environment.
JIPLET
Jiplet is short for Java SIP Servlet. The Jiplet Container is an open-source container for server-side SIP applications.
http://www.cafesip.org/projects/jiplet/index.html
SailFin
Project SailFin is based on robust and scalable SIP servlets technology on top of a deployment-quality, Java EE-based GlassFish. We are working towards achieving JSR 289 compatibility, adding high- availability and clustering features, and integrating with existing GlassFish services.
JSR 289 updates the SIP Servlets API and defines a standard application programming model to mix SIP Servlets and Java EE components. Java EE services, such as web services, persistence, security, and transactions, enable faster development of smarter communications-enabled applications.