Linux is a trademark of the Linux Foundation (see https://www.linuxfoundation.org/the-linux-mark/ https://www.linuxfoundation.org/the-linux-mark/), and as menti

Linux is a trademark of the Linux Foundation (see https://www.linuxfoundation.org/the-linux-mark/ https://www.linuxfoundation.org/the-linux-mark/), and as mentioned by others Firefox is a trademark of Mozilla. It's fairly common, and used to ensure a fork doesn't pop up and claim to be the original product.