Open source software cannot apply for patents because open source software must comply with the GNU protocol. GNU is anti-patent
GNU has something like this: Finally, every program is constantly threatened by software patents. Governments should not allow patents to restrict the development and use of general-purpose computer software, but in areas where governments do allow such things, we want to avoid the danger that patents applied to free software effectively privatize that software. To prevent this from happening, the General Public License ensures that no one can use patent rights to make free software non-free.