Effect
# emerge --ask sys-kernel/linux-firmware
…
!!! All ebuilds that could satisfy "sys-kernel/linux-firmware" have been masked.
!!! One of the following masked packages is required to complete your request:
- sys-kernel/linux-firmware-99999999::gentoo (masked by: || ( ) linux-fw-redistributable license(s), missing keyword)
…
# echo "sys-kernel/linux-firmware @BINARY-REDISTRIBUTABLE" >> /etc/portage/package.license
# emerge --ask sys-kernel/linux-firmware
…
Would you like to merge these packages? [Yes/No]
…