You’ve heard the saying. “Nobody ever got fired for buying IBM.” That mantra was first popularized in the 1970s, long before the advent of the personal computer changed the face of enterprise IT. Big iron was king — often in the form of IBM Corp. mainframes — and enterprise software was a big, big deal.

In those days, the Free Software Foundation was barely a glimmer in Richard Stallman’s eye. A full suite of enterprise applications meant an expensive, long-term contract, preferably with the largest (and hence most reliable) vendor you could find — somebody like IBM, for example.

A lot has changed since then, but some things remain the same. IBM still wants to be the go-to vendor for every enterprise’s IT needs. To secure that position in the 21st century, however, it’s had to learn to play a new ball game to suit today’s market.

“The size of the marketplace and the kinds of customers that we can address with technology is growing and moving into nontraditional areas,” says Doug Heintzman, director of technical strategy at IBM’s software group. “There’s a whole set of SMBs and new businesses and startups that, quite frankly, haven’t traditionally been IBM customers, that have different kinds of thresholds.”

What those businesses have in common is a need for greater flexibility and agility than traditional, monolithic IT infrastructures can provide. They’re also more risk-averse when it comes to IT expenditures. A smaller shop won’t pay for a big, expensive software suite that’s full of features it will never use, especially if it anticipates changing market conditions ahead.

What’s more, these concerns aren’t limited to SMBs and startups. Increasingly, even enterprise customers are demanding low-cost, low-overhead, flexible architectures that offer scalable performance without threatening to hamstring IT agility as a result of vendor lock-in.

At the root of this trend is the proliferation of mature, open, industrywide technology standards. Open standards level the playing field by enabling interoperability between competing products in a given software category, allowing customers to choose freely from among different vendors’ offerings. Standards also open the door for the open source community to create its own implementations in key software categories, which drives down customer IT costs even further.

“In many ways, we view open source, in many situations, as ‘open standards on steroids,’ ” Heintzman says. A standard merely describes a common protocol or format, but an open source implementation brings it to life.

IBM isn’t the only major software vendor to embrace open source and open standards as a means of appeasing agility-conscious customers; Hewlett-Packard Co., Novell Inc., Oracle Corp., and many others have joined suit. When Computer Associates International Inc. made its Ingres relational database open source last year, it very quickly realized a double benefit that lent new luster to a product that had previously been merely a reliable but unremarkable performer.

“It’s been very difficult for people to move data off their existing databases into other forms,” explains Tony Gaughan, senior vice president of product development at CA. By making Ingres open source, not only did CA give customers a very real cost incentive to switch databases, it also opened the door for the open source community to add features. One of the first major contributions to the product was an engine that allowed Ingres to understand Oracle’s proprietary PL/SQL query language, making it much easier for Oracle customers to migrate their applications to Ingres.

This trend toward openness, standardization, and flexibility isn’t limited to software. As Sun Microsystems Inc. can testify, customers are turning away from large, high-powered single machines in favor of scalable clusters of commodity, Intel-powered 1U and blade servers. Google Inc. is perhaps the greatest example of this new kind of architecture, boasting a datacenter composed of tens of thousands of PC-based servers coupled with fault-tolerant software.

True, IBM still sells mainframes; but its sales pitch has changed considerably since the 1970s. These days, IBM zSeries boxes run Linux in addition to z/OS, and mainframe processor units are billed as a way to quickly deploy virtual servers in a clusterlike configuration, using IBM’s z/VM virtualization software.

From the datacenter to the desktop, scalability, flexibility, openness, and standardization have become the watchwords of the new IT. The message for vendors: Watch out. If your products aren’t competitive, it may well be you who ends up getting fired.