Microsoft and Sun Microsystems have both signed Unix licensing agreements with the SCO Group in the past year.
The licensing agreements, which cover source code and patents contained in SCO's Unix operating system will net SCO a total of $13.25m, according to documents filed by SCO with the Securities and Exchange Commission.
Sun's licence is one of several it has signed with the various owners of the Unix System V source code, of whom SCO is the latest, since 1994, said John Loiacono, the vice president of Sun's operating platforms group.
The most recent licence, signed in February of this year, "licensed several hundred drivers to connect, essentially, peripheral devices to the operating system", he added.
Microsoft announced a similar licensing deal with SCO in May - a move that some industry observers interpreted as supporting SCO's breach of contract lawsuit with IBM.
Sun's agreement can be seen in a similar light, according Harry Fenik, the president of industry consulting firm The Sageza Group. "I would wager that Sun saw this as an opportunity to bolster a comrade in arms," he said. "From Sun's perspective right now, the big enemy is IBM."
Sun's Loiacono disagreed. "The motivation we have is very different from what they have for licensing," he said. "I never want to be lumped into any categories with Microsoft other than profitability."
The licensing deal with Sun provides SCO with the funds to prolong its lawsuit with IBM, and not because it indicates that Sun recognises the validity of SCO's legal claims, Fenik said.
"I don't think it's meaningful at all. [Sun] made a buy versus build decision [for Solaris x86 Platform Edition] to get access to a bunch of drivers for contemporary versions of Intel hardware."
Because Sun purchased strong intellectual property rights with this and the various other Unix System V licences it has signed with SCO over the past decade, it can now indemnify users of its Solaris x86 against lawsuits, Loiacono said.
"I have a different licence than what IBM purchased," he said. "I wanted complete ownership of my IP, so I bought IP rights outright."
IBM has repeatedly stated that it would "stand by" users of its AIX operating system, who appear to be threatened by the lawsuit, but it has stopped short of saying it would indemnify them.
Whether or not IBM had signed a licence similar to Sun's would have had no bearing on SCO's lawsuit, according to SCO spokesman Blake Stowell.
"It doesn't really pertain to whether IBM purchased an additional licence or not. What it really comes down to is whether they honoured their contract or not," he said. "This isn't blackmail money."
Robert McMillan writes for IDG News Services