license: Add a non applicable (NA) license only for metaports

[bapt]

Summary

Make sure in the framework it cannot be used elsewhere than metaports

PR: 223932

[tcberner]

Mk/bsd.licenses.db.mk

80

^ shouldn't that read:
# "Non Applicable" for metaports

otherwise, one reads it as "This is not applicable for metaports" -- which is the opposite of what it is :D

Mk/bsd.licenses.mk

215

^ could you please add parentheses to make operation precedence of && and || explicit?

[bapt]

See D36358