You don't even have to go to open source. You can see this hostile behaviour from their top-paying clients!
Microsoft own previous gen Xbox emulator on the next gen xbox (i think it was original xbox emulated in the 360, but i might be wrong) was impacted by the team having to reverse-engineer the GPU because nvidia refused to let the emulator people to have access to the documentation provided to the original team.
Microsoft own previous gen Xbox emulator on the next gen xbox (i think it was original xbox emulated in the 360, but i might be wrong) was impacted by the team having to reverse-engineer the GPU because nvidia refused to let the emulator people to have access to the documentation provided to the original team.