Linux

About fifteen years ago, Microsoft felt threatened by Linux's growing market share, and decided to team up with/outright buy patent trolls and use the new portfolio of around 230 patents to claim that the Linux distributions were infringing on Microsoft's intellectual property and potentially sue them.

As Red Hat and other FOSS companies entrenched in their positions and geared up for a long and expensive legal fight, SuSE saw an opportunity to displace Red Hat, and threw everybody under the bus by saying something like, "Yes, Linux absolutely infringes on Microsoft patents. We will pay you for using your IP if you shield us from litigation."

So that threw out the entire argument that Linux did not infringe on Microsoft patents because you had the second biggest Linux company saying it was true and the right thing to do was to pay Microsoft for all of their wonderful contributions. So Microsoft did this kind of mobster thing where they let SuSE pay them for "protection" from lawsuit, and then used this as precedent that the other Linux distributors weren't playing fairly unless they also paid for patent use. And SuSE hoped that this would result in only Novell/SuSE being the legal Linux to buy in the market and everybody would run to them with open arms. Kind of a dick move.

This emboldened Microsoft, and resulted in lawsuits from Microsoft over things like, accessing the FAT filesystem from a Linux device (TomTom, at the time GPS device company) and is historically the reason that Nexus phones (which became Google Pixel phones) never came with SD card expansion (so they wouldn't be accessing a FAT filesystem from Linux). So for the next half decade or so, Microsoft decided to just start suing everybody over patent infringement, and this is how the smartphone era was born and why it is really difficult to do things that would be obvious on a computer -- smartphone designers had to invent new ways, even if obtuse, to get around patents.

In 2018 Microsoft decided that they needed Linux, and ended hostilities by giving the patent portfolio (now up to 60000+ patents) to a consortium of companies called Open Innovation or something like that, that was originally designed to share patents freely without litigation in response to Microsoft's aggressive behavior a decade earlier.