According to CEO Dave Rosenberg, Mule is a classic “bottom up” approach to ESB that was designed simply as high performance transaction brokering and transformation middleware, period. The entire downloadable is only about 50 Mbytes, and is written in pure Java and XML.

New features in the latest version include support for Apache CXF web services framework, which simplifies development of web services from the Java JAX-WS interface using different protocols, ranging from SOAP to simple XML over HTTP, RESTful HTTP, or even CORBA, plus support of transports such as HTTP, JMS, or JBI.

The new version also adds patch management using MuleHQ, plus a beta version of the new Mule Saturn business activity monitoring dashboard for showing if transactions traveling through Mule are actually consumed at the endpoints. The idea behind Saturn is that each transaction that travels through Mule has a unique identifier and can be tracked. That means that Saturn can report workflow and state, process visualization, drill-down and root-cause analysis, and reporting on service-level agreements.

But the highlight of the new release is Mule Galaxy, a new no-frills registry and repository governance tool that the company claims comes with a fraction of the overhead (and cost) of more established offerings such as HP’s Systinet. It provides the usual spate of lifecycle management of services, dependency management, and querying and indexing features. More importantly, consistent with Mule’s stripped-down design, it is accessible through RESTful web service requests (a simpler alternative to SOAP when making requests for data retrieval web services), and can publish changes using simple Atom syndication.

The company, which has drawn roughly $15 million in two rounds of funding, is now beginning to raise its profile. They are doing so with an approach that seeks to counter the household names with an approach not unlike Red Hat of five years ago.

While the so-called “mainstream” of ESB development has tended to treat ESB as a checkbox feature of the classic all-purpose, enterprise SOA platform, the Mule project is a minimalist approach that is intended to support one and only one goal: deliver high performance without all the programming overhead. “We start with an 80/20 solution,” said Rosenberg, summarizing the company’s approach.

Consistent with that approach is the company’s Red Hat-like strategy that pushes both community and commercial product, and with this week’s announcement, availability of ESB on demand through a Software-as-a-Service model via the Internet.

Evidence of Mule’s back-to-basics approach can be found in the development tools for the offerings, which de-emphasize splashy GUIs in favor of the no-nonsense approach that code-oriented developers (in the UNIX tradition) have always demanded. Installs tend to be very modular. In place of the single galactic ESB, many of Mule’s customers take federated approaches, with at least one well-known global financial service firm running 75 instances.

The result is that Mule has drawn a modest but very high-profile following for transaction-intensive installs. Starting with Wal-Mart.com as its cornerstone reference account, other references count AOL, which uses Mule as a distributed data ETL (extract, transform, and loading) tool; and Major League Baseball, which uses Mule to push game scores and statistics out using RESTful web services.

Although there are only about 50 paying customers, Mule has about 2000 production installs, which is arguably on par with better-known rivals like Tibco. It is now seeking to complement high-end reference installs with entry-level integration-as-a-service subscriptions to organizations that would normally consider ESBs as being too complicated for them.

Mule’s strategy to make integration simpler is parallel with other providers like Cast Iron Systems, which packages commodity ETL in an appliance. But with its geek-like programmer appeal (no fancy GUIs here), Mule’s approach couldn't be more different from BPM providers like Lombardi, that seek a form of white-board level integration that is intelligible to a business analyst.

The Mule 1.5 ESB is available now, while the general release of Mule Galaxy should come in Q2.

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