Unspecified patents not actually licensed

"Limited patent license. Realtek Semiconductor Corporation
grants a world-wide, royalty-free, non-exclusive license
under patents it now or hereafter owns or controls to make,
have made, use, import, offer to sell and sell ("Utilize")
this software, but solely to the extent that any such patent
is necessary to Utilize the software alone, or in combination
with an operating system licensed under an approved Open
Source license as listed by the Open Source Initiative at
http://opensource.org/licenses.  The patent license shall
not apply to any other combinations which include this
software.  No hardware per se is licensed hereunder."
/usr/src/sys/contrib/dev/rtwn/LICENSE

Obviously FreeBSD isn't licensed under an OSI-approved
license.