I'm not sure what alternatives you want? If you mean transport protocol, then you could look at FTP. Also, we'll have SOAP integration in JBossESB 4.2 due in May. There may be preliminary releases of that before then.
This architecture intends to use Apache axis to implement SOAP <-> JMS part of the protocol stack. I would like to know about any other implementations possible ? I know that the SOAP <-> JMS <-> HTTP/S part can be replaced by just JMS and also by XML <-> JMS <-> SSL. I would like to know if there are any such engines available and are they suitable for this scenareo at all considering the fact that all we want is assured asynchronous messaging between JBossESBs.
JMS is probably your best bet at the moment. Reliable message delivery is a tricky subject in general. We intend to support reliable (and asynchronous) delivery over a range of protocols, but we're not there yet. BTW, you do realise that true asynchrony is maybe not what you want, since you cannot reason about the completness of any distributed system (ESB or not) in that event?