Current open source  ESB offerings include Mule, Synapse, Celtix, ServiceMix, JBossESB, and Open ESB. Among the considerations you¢ll want to take into account when evaluating an ESB are these:
Level of commitment to standards: certain projects are built from the ground up in order to conform to and support certain standards (e.g., ServiceMix with JBI and Synapse with the WS-* specifications). Others, like Mule, are more agnostic with respect to standards, supporting them but not dogmatically. You may want to choose your ESB based on your own level of commitment to standards.

Platform support: you¢ll of course want to consider whether the ESB you¢re thinking of using supports the platforms (application servers, web  servers, messaging middleware, application frameworks) you¢re already using.



Regarding requirements that you mentioned ,I think the best solution  is Mule.