non GPL format option

docs/spelling-wordlist.txt

@@ -39,3 +39,4 @@ HD
 
 Berman
 Freenode
+GPL

docs/validate.rst

@@ -321,14 +321,26 @@ to validate. Their names can be viewed by inspecting the
 `FormatChecker.checkers` attribute. Certain checkers will only be
 available if an appropriate package is available for use. The easiest way to
 ensure you have what is needed is to install ``jsonschema`` using the
-``format`` setuptools extra -- i.e.
+``format`` or ``format_nongpl`` setuptools extra -- i.e.
 
 .. code-block:: sh
 
    $ pip install jsonschema[format]
 
-which will install all of the below dependencies for all formats. The
-more specific list of available checkers, along with their requirement
+which will install all of the below dependencies for all formats.
+
+Or if you want to install MIT-license compatible dependencies only:
+
+.. code-block:: sh
+
+   $ pip install jsonschema[format_nongpl]
+
+The non-GPL extra is intended to not install any direct dependencies
+that are GPL (but that of course end-users should do their own verification).
+At the moment, it supports all the available checkers except for ``iri`` and
+``iri-reference``.
+
+The more specific list of available checkers, along with their requirement
 (if any,) are listed below.
 
 .. note::
@@ -342,7 +354,7 @@ Checker                    Notes
 =========================  ====================
 ``color``                  requires webcolors_
 ``date``
-``date-time``              requires strict-rfc3339_
+``date-time``              requires strict-rfc3339_ or rfc3339-validator_
 ``email``
 ``hostname``
 ``idn-hostname``           requires idna_
@@ -353,9 +365,9 @@ Checker                    Notes
 ``json-pointer``           requires jsonpointer_
 ``regex``
 ``relative-json-pointer``  requires jsonpointer_
-``time``                   requires strict-rfc3339_
-``uri``                    requires rfc3987_
-``uri-reference``          requires rfc3987_
+``time``                   requires strict-rfc3339_ or rfc3339-validator_
+``uri``                    requires rfc3987_ or rfc3986-validator_
+``uri-reference``          requires rfc3987_ or rfc3986-validator_
 =========================  ====================
 
 
@@ -365,7 +377,8 @@ Checker                    Notes
 .. _rfc5322: https://tools.ietf.org/html/rfc5322#section-3.4.1
 .. _strict-rfc3339: https://pypi.org/pypi/strict-rfc3339/
 .. _webcolors: https://pypi.org/pypi/webcolors/
-
+.. _rfc3339-validator: https://pypi.org/project/rfc3339-validator/
+.. _rfc3986-validator: https://pypi.org/project/rfc3986-validator/
 
 .. note::
 

jsonschema/_format.py

@@ -248,7 +248,27 @@ def is_idn_host_name(instance):
 try:
     import rfc3987
 except ImportError:
-    pass
+    try:
+        from rfc3986_validator import validate_rfc3986
+    except ImportError:
+        pass
+    else:
+        @_checks_drafts(name="uri")
+        def is_uri(instance):
+            if not isinstance(instance, str_types):
+                return True
+            return validate_rfc3986(instance, rule="URI")
+
+        @_checks_drafts(
+            draft6="uri-reference",
+            draft7="uri-reference",
+            raises=ValueError,
+        )
+        def is_uri_reference(instance):
+            if not isinstance(instance, str_types):
+                return True
+            return validate_rfc3986(instance, rule="URI_reference")
+
 else:
     @_checks_drafts(draft7="iri", raises=ValueError)
     def is_iri(instance):
@@ -280,15 +300,19 @@ def is_uri_reference(instance):
 
 
 try:
-    import strict_rfc3339
+    from strict_rfc3339 import validate_rfc3339
 except ImportError:
-    pass
-else:
+    try:
+        from rfc3339_validator import validate_rfc3339
+    except ImportError:
+        validate_rfc3339 = None
+
+if validate_rfc3339:
     @_checks_drafts(name="date-time")
     def is_datetime(instance):
         if not isinstance(instance, str_types):
             return True
-        return strict_rfc3339.validate_rfc3339(instance)
+        return validate_rfc3339(instance)
 
     @_checks_drafts(draft7="time")
     def is_time(instance):

setup.cfg

@@ -41,6 +41,12 @@ format =
     rfc3987
     strict-rfc3339
     webcolors
+format_nongpl =
+    idna
+    jsonpointer>1.13
+    webcolors
+    rfc3986-validator>0.1.0
+    rfc3339-validator
 
 [options.entry_points]
 console_scripts =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{35,36,37,38,py,py3}-{build,tests}
+    py{35,36,37,38,py,py3}-{build,tests,tests_nongpl},
     demo
     readme
     safety
@@ -22,8 +22,9 @@ whitelist_externals =
     virtualenv
 commands =
     perf,tests: {envbindir}/python -m pip install '{toxinidir}[format]'
+    tests_nongpl: {envbindir}/python -m pip install '{toxinidir}[format_nongpl]'
 
-    tests: {envbindir}/trial {posargs:jsonschema}
+    tests,tests_nongpl: {envbindir}/trial {posargs:jsonschema}
     tests: {envpython} -m doctest {toxinidir}/README.rst
 
     perf: mkdir {envtmpdir}/benchmarks/
@@ -53,7 +54,7 @@ deps =
 
     perf: pyperf
 
-    tests,coverage,codecov: -r{toxinidir}/test-requirements.txt
+    tests,tests_nongpl,coverage,codecov: -r{toxinidir}/test-requirements.txt
 
     coverage,codecov: coverage
     codecov: codecov