No, we wouldn't. Linux climbed its way up to overtake proprietary UNIX despite being less capable, which it very much was at the time.
Linux came around at the right time when the Internet was going public and regular people had access to hardware that could run a decent UNIX. People latched onto it because it was free and an interesting project. The free BSDs were just late enough to the party that they missed out on the momentum.
All the proprietary UNIX vendors (other than SCO) relied on expensive proprietary hardware sales. Intel ate their lunch while they were too busy stabbing each other in the back to notice. Linux killed SCO because SCO was, quite frankly, overpriced crap.
None of this had anything to do with the license, other that the fact you could use it for free. It was all about hardware availability, the rise of the Internet, the wave of new IT people who had experienced Linux at home, and the fact that Linux on Intel was good enough to replace those pricy proprietary machines.
Now, you wanna talk Apple, there's where your code "theft" kicks in. But that's a whole different thing.
The three companies you list are horrible examples. IBM is kind of a UNIX vendor, sort of, but not like Sun or DEC. They sell solutions, and the solutions that use AIX don't overlap with what Linux was capable of in 1998. I'd argue that, given their complete disregard for Tru-64 and pretty much all things DEC, Compaq was never a UNIX vendor - they just inherited a bunch of legacy systems they needed to support. They certainly didn't push for new Tru-64 based systems. Oracle wasn't a UNIX vendor at all and wouldn't become one for quite some time.
BSD sockets are also a bad example. They were the reference implementation, paid for by DARPA. The entire purpose of BSD sockets was to be copied into other operating systems. You'll notice that Linux copied them as well.
IBM and Compaq invested in Linux because they wanted something that ran on their lower-end server hardware and could handle web traffic. Oracle invested in Linux because they wanted to be the backend to all these new websites that were cropping up.
IBM, Oracle, and Compaq didn't give a rat's ass about the operating system code - they wanted the platform. If Linux had never happened and FreeBSD became the new hot thing all the online hackers were talking about, the result would have been exactly the same. They'd have poured money into the projects rather than trying to make their own thing because that's the financially sensible thing to do. The UNIX wars were over, and proprietary software lost.
Meanwhile, the last major UNIX vendor - Sun Microsystems - was giving away its own source code under the CDDL. FreeBSD ended up adopting a lot of it. That's the complete opposite effect from what you're talking about.
Sun got involved in the GNOME project and even deprecated their own CDE desktop in favor of it. Was it because it was GPL? No. It was because they saw that all the new desktop software was coming out of the Linux community, who didn't have access to CDE. Even if GNOME had been BSD licensed they would still have switched to it, because they were still trying to keep the workstation market alive at that point and CDE was quickly becoming irrelevant.
As far as I can see, the only companies interested in taking operating system code were the network appliance vendors and Apple. It only worked for them because they didn't care about compatibility.
Linux came around at the right time when the Internet was going public and regular people had access to hardware that could run a decent UNIX. People latched onto it because it was free and an interesting project. The free BSDs were just late enough to the party that they missed out on the momentum.
All the proprietary UNIX vendors (other than SCO) relied on expensive proprietary hardware sales. Intel ate their lunch while they were too busy stabbing each other in the back to notice. Linux killed SCO because SCO was, quite frankly, overpriced crap.
None of this had anything to do with the license, other that the fact you could use it for free. It was all about hardware availability, the rise of the Internet, the wave of new IT people who had experienced Linux at home, and the fact that Linux on Intel was good enough to replace those pricy proprietary machines.
Now, you wanna talk Apple, there's where your code "theft" kicks in. But that's a whole different thing.