The foundation said that 15 GNU software components will be released under GPL 3 on Friday, and the rest of the GNU software will follow in coming months. But some are being more cautious.

The primary consideration in moving the MySQL database software to GPL 3 is whether the new version will be adopted, said Kaj Arnö, vice president of community for the company.

"We're happy about many changes in text," Arnö said. "What still remains to be seen is the adoption. GPL 3 is still something people are asking questions about. Our logic is that we don't want to be those that answer those very first questions."

Sun Microsystems, which selected GPL 2 to govern Java and, more unusually, the UltraSparc T1 processor design, is still evaluating the license, said Chief Open Source Officer Simon Phipps. He did call GPL 3 "a strong and market-changing document," however.

Those who create software have some digesting to do, but for those who just use open-source software, GPL 3 will soon become routine, said James Harvey, an intellectual property attorney for Hunton & Willams and legal adviser to what he described as some of the largest companies using Linux today.

"Once end users spend time with this license, they will get more and more comfortable with it, and it will become another primary license in their open-source rotation," he said.

Lowered barriers
In many cases, GPL software has been explicitly licensed under GPL version 2 or later, in which case a programmer's software may be used in a project governed by both. But in cases where software is governed only by one or the other, there's a risk that software can't be moved back and forth, leaving code on separate islands.

One area that's a risk is with Linux and Solaris, Sun's version of Unix that's now becoming an open-source project under a different license, the Community Development and Distribution License. Sun Chief Executive Jonathan Schwartz said in May that he hopes GPL 3 could let Sun "converge on a uniform license."

And there might be room for compromise: Torvalds said that a GPL 3 Solaris could coax him toward a GPL 3 Linux kernel. "I don't think the GPL 3 is as good a license as (GPL) 2, but on the other hand, I'm pragmatic, and if we can avoid having two kernels with two different licenses and the friction that causes, I at least see the reason for GPL 3," he said earlier this month.

The license barrier is less of an issue when, as is commonly the case, separate projects are in different domains and source code isn't tightly linked, as for example is the case with MySQL running atop Linux.

The new GPL also lowers barriers. For example, it's now compatible with the Apache License, a feature that pleases Jeremy Allison, one of the lead programmers behind Samba, a widely used file-server software project that's governed by the GPL. "Nothing is perfect," he said, but added, "I hope to see wide adoption of the GPLv3."

Broader GPL compatibility in GPL 3 will make life easier for MySQL if the company moves to the new license, Arnö said. The MySQL database itself is under GPL, but so is "client" software that's used in other software that access the database. That's been a thorny issue because PHP, a project under a different open-source license, often is used in conjunction with MySQL databases and uses that client software.

The license initially was written by a programmer, but it's become decidedly more lawyer-oriented. For example, the provision regarding the Novell-Microsoft pact reads in part, "You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007."

"The license has gotten much easier for lawyers to deal with and probably not as easy for engineers to deal with," Harvey said.

But the legalese isn't entirely inappropriate, because lawyers at multibillion-dollar corporations now routinely deal with it. The GPL has moved into the mainstream.