Microsoft Open Source Blog 
Microsoft recently joined the Open Invention Network (OIN), a community dedicated to protecting Linux and other open source software programs from patent risk. Since its founding in 2005, OIN has been at the forefront of helping companies manage patent risks and we’re humbled to be a part of it.
It’s been great to see the reaction from open source community members to the news, including good questions coming our way about what our membership means for developers. We caught up with Microsoft’s Erich Andersen to get more details around some of the frequently asked questions.
Q: What led Microsoft to join the OIN?
Joining OIN reflects Microsoft’s patent practice evolving in lock-step with the company’s views on Linux and open source more generally. We began this patent evolution over two years ago through programs like Azure IP Advantage, which extended Microsoft’s indemnification pledge to open source software powering Azure services.
Q: What is and isn’t included in the OIN license?
Microsoft’s entire patent portfolio is subject to the terms of the OIN license, which covers the Linux System defined by OIN here. Today this portfolio numbers 60,000 patents.
Q: How can OIN members now use Microsoft’s patents?
All OIN members – all 2,650 licensees – receive a patent license from Microsoft. This means they are free to make, use or distribute Linux System technology with the benefit of a royalty-free license from Microsoft.
Q: What was the process like to join?
Joining OIN was an easy process – there is a click-through license available on the organization’s web site. We executed the license on the OIN website like any other member.
Q: By joining OIN, is Microsoft “open sourcing” or “donating” its patents to OIN?
No, Microsoft is granting a royalty-free patent license for the benefit of other OIN members. Like other OIN member companies, Microsoft continues to own its patents. As part of this announcement, Microsoft did not donate patents to OIN.
Additional questions? Let us know in the comments.