SOA. There are many popular open source software solutions available for SOA. Open source is making incredible inroads into software infrastructure and SOA middleware is no exception. Open source software thrives where standards exist and SOA has plenty -- some would say too many! There is a great variety of open source SOA solutions available, ranging from message queues to data transformation, application adaptors to orchestration engines, and most notably the ESBs, Web services solutions and SOA stacks that contain many middleware components. JBoss. FUSE.