When you look for "WSO2 Alternative" you need to be precise on which space of WSO2 that you are looking for alternatives.
WSO2 has a complete enterprise middleware stack as well as the same middleware platform as a cloud computing platform as a service offering.
The middleware platform stack, include products such as
- Application Server
- ESB
- Business Process Server
- and more...
There are loads of Apache projects that the WSO2 products are based on, such as Apache Axis2, Apache Synapse, Apache Tomcat, Apache ODE, Apache Rampart and the like.
One can use these base projects of the WSO2 and use those as alternatives to achieve various aspects of the platform.
You can also use the Eclipse Equinox and P2 projects, used as the base OSGi platform to facilitate the plug and play architecture of WSO2 Carbon base platform.
Note that, all of the products from WSO2 come with Apache 2.0 license.
If you are looking for alternatives other than Apache compatible license, in open source space, you can look for individual products aspects like ESB or BPEL or Application Server.
Some examples:
- ESB alternatives: FUSE, Mule
- BPEL : Intalio BPM Server
If you are looking for proprietary alternatives to WSO2 middleware stack you need to look for...
- IBM
- Oracle
- Redhat
In the cloud space, a good comparison of the cloud Java Platform as a Service on WSO2 offerings and others can be found at: http://wso2.org/library/articles/2011/08/comparison-wso2-stratos-other-paas-offerings
That article compares some of the alternatives such as
- Google App Engine
- Amazon Beanstalk
- CloudBee's Run@Cloud
with WSO2 StratosLive.
