Some code is so old that it predates the "invention" ( ) of free software by the FSF. Such an example is the RPC code provided by Sun to the world under a permissive license in 1984 and it was use in many implementations like the one used in Linux to provide NFS services. This was possible due to the licensing Sun choose at that time:
Sun RPC is a product of Sun Microsystems, Inc. and is provided for
unrestricted use provided that this legend is included on all tape
media and as a part of the software program in whole or part. Users
may copy or modify Sun RPC without charge, but are not authorized
to license or distribute it to anyone else except as part of a product or
program developed by the user.
However it isn't technically free software, as it was freeded before free software was formally defined ... and out of some strange reasons, people found the license now free enough. In some Linux distributions this situation was considered as a serious bug (I would file a bug against something different in regard of this, but that's a different story ) However due to whatever reasons, this particular issue wasn't resolved for years ...

As Tom Callaway wrote in a recent blog entry, this situation has been resolved now:
So, we restarted the effort with Oracle, and on August 18, 2010, Wim Coekaerts, on behalf of Oracle America, gave permission for the remaining files that we knew about under the Sun RPC license (netkit-rusers, krb5, and glibc) to be relicensed under the 3 clause BSD license.
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