 Because of licensing concerns , the OpenBSD team has re @-@ implemented software from scratch or adopted suitable existing software . Of particular note is the development , after license restrictions were imposed on IPFilter , of the pf packet filter , which first appeared in OpenBSD 3 @.@ 0 and is now available in other major BSDs . OpenBSD developers have also replaced GPL licensed tools ( such as diff , grep and pkg @-@ config ) with BSD licensed equivalents . 
