Following (what I hope was) consensus among pkgsrc developers, I
clarified how LICENSE is handled in the pkgsrc guide:

http://www.netbsd.org/Documentation/pkgsrc/fixes.html#handling-licenses

Basically, Open Source (OSI) and Free (FSF) licenses do not cause
LICENSE to be set, and other licenses should be added to
pksrc/licences and referred to.  Setting LICENSE to "shareware"
etc. is deprecated because it is imprecise and there is no way to
denote having paid a fee for the use of one package but not all
shareware programs.

Thomas Klausner has already added a number of licenses and removed
some uses of deprecated LICENSE=, and I removed LICENSE from graphviz
because it has an OSI-approved license (this was the impetus for
clarifying LICENSE guidelines).

I wondered about the Debian Free Software Guidelines as another
arbiter of generally-acceptable licenses, but have not come across a
reason to need to add that.

A similar issue perhaps exists with RESTRICTED, described at:

http://www.netbsd.org/Documentation/pkgsrc/fixes.html#restricted-packages

RESTRICTED is about redistribution of non-modified sources and binary
packages (which may include patches from pkgsrc), which is a subtly
different issue from install/use (covered by LICENSE).  I don't see a
problem with the current RESTRICTED mechanism and intent, although I
think it would be good to tighten up the language, clarifying that

  For CDROM, the variable should be set if it's not permissible to
  include the file on CDROMs that are sold, even for a profit.

  For FTP, the varible should be set if it's not permissible to make
  the file available at no charge over the Internet (by whatever
  protocol).

I think this is the intent already, but that's not what the words say
now.  Let me know if anyone has objections to the clarifications
above.