Red Hat has praised Microsoft's contribution of code to the Linux community this week, while still having a dig at the company whose Windows software resides on the desktops of 96 percent of corporate PCs.
The open source company urged its rival to pledge that it will never use its patents against Linux.
In a write-up by the Red Hat legal team on Tuesday, Red Hat emphasised Microsoft's change in behavior, in which Microsoft offered up 20,000 lines of code for Linux drivers linking Linux to Microsoft virtualization software.
But Microsoft needs to go a step further and promise to not use any patents against Linux, Red Hat's legal team said.
"Patent threats are irreconcilable with the norms and values that are at the heart of Linux. To win the respect and trust of the Linux community, Microsoft should unequivocally disavow such conduct and pledge that its patents will never be used against Linux or other open source developers and users.
Microsoft in the past has claimed Linux and open source software violated 235 patents and that users of open source software owed royalties to Microsoft.
A Microsoft official responded Wednesday that there is a balance between contributing to open source projects and insistence on respect for intellectual property.
"Some observers question how a company can contribute to open source projects while, at the same time, insisting on respect of its intellectual property rights by its competitors," said Horacio Gutierrez, Microsoft corporate vice president and depty general counsel, in a Microsoft blog entry. "In fact, these two things are not inconsistent, and striking a balance between them is one of the key things every commercial technology company must do in order to compete effectively in a mixed source world."
Microsoft on Tuesday made a further GPL contribution with the release of Microsoft Live Services Plug-in to integrate the company's [email protected] services with the Moodle course management system.