What does this whole patent thing mean? I'm not well-versed at all about licenses and patents and the technical jargon of the file is mostly non-sense to me. Would someone care to simply explain what this implies?
Most popular open source licenses (except GPLv3 and Apache) only give you a copyright license to the code, they do not give you a patent license. In theory, somebody could create some software, get a patent for it, release it under the BSD license or equivalent, and then sue everybody who uses the software for patent infringement.
However, some lawyers believe that the BSD and similar licenses give you an implicit patent grant. The licenses say you have a license to use the software. Since you cannot use the software without a patent license, then giving somebody a license to use the software automatically includes patent rights.
The inclusion of an explicit patent grant means that the implicit patent grant is no longer necessary and therefore no longer exists. So you had armchair lawyers divided into two camps. The first weren't so sure about that implicit license thing, so Facebook's inclusion of an explicit grant was a good thing. The second camp noticed a few problems with the explicit grant, and complained loudly that the explicit grant was worse than the previous implicit grant.
With these changes, Facebook addresses the criticisms of the second camp.
From what I can understand from [1][2][3], is the previous patent clause meant that if you and Facebook got into patent litigation, any open source software you used that was written by Facebook would be revoked (opening you up to a license breach). This was scary because Facebook owns a ton of patents and if Zuckerberg woke up on the wrong side of the bed one morning and decided to sue everyone with their portfolio of patents, it would be impossible to countersue if you used any Facebook code. The other posts go into how companies like Google and Facebook use patents as a way of ensuring mutually assured destruction, and if Google had used Facebook code under the license it would be like Google disarming all their nuclear bombs against facebook.
IANAL, but it seems the new license is a bit more GPL-esque in its restrictions by saying if you use this software than you cannot sue Facebook, its subsidiaries, and your parent weapon of choice can't be based off Facebook software (or else you lose the software license). However if Facebook sues you, then you don't lose the license and you are free to counter sue facebook with your nuclear arsenal of patents.
The reason I call it GPL-esque is it seems to introduce restrictions on how you can legally use the software once you've incorporated it (like how the GPL prevents you from not redistributed the source code), the Facebook license seems to prevent you from launching patent claims that are built off Facebook software. My guess is that if enough people used this license it would be difficult to litigate anyone else without revoking some of your software licenses.
Finally, I never took a law class a day in my life and the closest domain knowledge is an intro to econ class I took in freshman year of college so I could 100% wrong.
