Unlike with the photos or illustrations, there are not that many websites where you can find quality videos, licensed under public domain or Creative Commons Zero license, free for commercial use.
You can find free videos all over the internet, but they are usually licensed under CC3 or CC-By licenses, require attribution or imposing other limitations. CC0 video websites are rare.
If you need free photos for commercial use, check this out: 7 websites to get free images for commercial use. And if you need free vectors and illustrations for commercial use, check this out: 7 websites to get free vectors and illustrations for commercial use. To find free music and audio files for commercial use, check this out: 5 websites to get free music and sounds for commercial use.
CC0 is the only Creative Commons license compatible with GPL license. So, here are 5 websites with high-quality videos, all under Public Domain or CC0 license, and free for commercial use, with no attribution required.
Use comments to let me know if you have some other CC0 videos websites to recommend.