Linux Weekly News writes . . .

“Real-time Linux is patented. Some RTLinux users have been surprised that the RTLinux concept is subject to patent number 5995745, held by veteran RTLinux hacker Victor Yodaiken. This patent was issued on November 30, 1999, and covers:

• providing a real time operating system for running real time tasks and components and non-real time tasks;
  
• providing a… general purpose operating system as one of the non-real time tasks;
  
• preempting the general purpose operating system as needed for the real time tasks;
  
• preventing the general purpose operating system from blocking preemption of the non-real time tasks.”

“In other words, if you're working with a real-time operating system that is attached to a general purpose system, you're treading on this patent's turf. Of course, there may be some prior art problems – one could say that VMS did all of the above 20 years ago.”

“Mr. Yodaiken's plans for the patent are evidently being worked out in cooperation with Linux International and Linus Torvalds. The components of those plans, according to his posting on the subject, would appear to include:

• Users of RTLinux need not pay any royalties as a result of this patent.
  
• Users of other real-time add-ons for Linux need not pay royalties, but only if (1) the add-on is explicitly labeled as being (or not being) compatible with RTLinux, and (2) the add-on is released under the GPL.
  
• Non-open projects will have to pay. It is not clear what the status is for non-Linux free projects, such as one based on one of the BSD variants.”

“Mr. Yodaiken has done the Linux community a great deal of good through his RTLinux work. And it is good that he is keeping things open for the Linux community. But the use of software patents, even for a 'good cause,' is a bit troublesome. Software patents are a double-edged weapon at best, and any embracing of them by the free software community is likely to lead to trouble.”

The RTLinux patent can be viewed * here *.

 
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