Microsoft Corp. has suggested in recent years that companies using the Linux computer-operating system might be violating Microsoft patents. Now, in an effort to avert any legal threat that might discourage the adoption of Linux, a group of Microsoft rivals is about to acquire a set of patents formerly owned by the software giant.

Linux is a free open-source operating system that has gained ground against Microsoft's Windows software among business users, especially in servers, the big back-office computers inside companies....