Microsoft and the Linux Foundation have joined forces over proposed changes in the law regarding software contracts.

In a joint letter (PDF) to the American Law Institute (ALI) the two organisations raise concerns over the draft Principles of the Law of Software Contracts that the ALI is working on.

The key issue is a guideline that would make the assumption that all software should be shipped with no defects, and that this should be considered a de facto warranty.

"The mere fact that the Linux Foundation and Microsoft are joining forces may be viewed by some as remarkable, given that our differences receive far more public attention than when our interests converge," wrote Horacio Gutierrez, corporate vice president and deputy general counsel of intellectual property and licensing at Microsoft, in a company blog.

"But there is a wide range of issues that affect all software developers alike. Our industry is diverse and sometimes contentious, but if nothing else unites us it is that we all believe in the power of software."

The two organisations have asked for more time to study the implications of the plan and to offer advice to the ALI.

The ALI is a collection of the American legal establishment which draws up guidelines for judges that explain how the law should be applied in legal cases. The group is meeting this week to finalise the Principles of the Law of Software Contracts.

"The principles outlined by the ALI interfere with the natural operation of open source and commercial licences, as well by creating implied warranties that could result in a tremendous amount of unnecessary litigation, which would undermine the sharing of technology," said Jim Zemlin, executive director of the Linux Foundation, in his blog.