diff -ruN a/pdm/pep517/base.py b/pdm/pep517/base.py
--- a/pdm/pep517/base.py	2022-08-06 17:29:41.927385300 +0200
+++ b/pdm/pep517/base.py	2022-08-23 17:45:23.391722696 +0200
@@ -7,7 +7,7 @@
 from pathlib import Path
 from typing import Any, Iterator, Mapping, TypeVar, cast
 
-from pdm.pep517._vendor import tomli
+import tomli
 from pdm.pep517.exceptions import MetadataError, PDMWarning, ProjectError
 from pdm.pep517.metadata import Metadata
 from pdm.pep517.utils import is_python_package, safe_version, to_filename
diff -ruN a/pdm/pep517/license.py b/pdm/pep517/license.py
--- a/pdm/pep517/license.py	2022-08-06 17:29:41.927385300 +0200
+++ b/pdm/pep517/license.py	2022-08-23 17:45:23.391722696 +0200
@@ -1,6 +1,6 @@
 import warnings
 
-from pdm.pep517._vendor.license_expression import (
+from license_expression import (
     LicenseSymbol,
     Licensing,
     get_spdx_licensing,
diff -ruN a/pdm/pep517/metadata.py b/pdm/pep517/metadata.py
--- a/pdm/pep517/metadata.py	2022-08-06 17:29:41.927385300 +0200
+++ b/pdm/pep517/metadata.py	2022-08-23 17:45:23.391722696 +0200
@@ -5,7 +5,7 @@
 from pathlib import Path
 from typing import Any, Callable, Generic, Iterable, Mapping, TypeVar, cast
 
-from pdm.pep517._vendor.packaging.requirements import Requirement
+from packaging.requirements import Requirement
 from pdm.pep517.exceptions import MetadataError, PDMWarning, ProjectError
 from pdm.pep517.license import normalize_expression
 from pdm.pep517.utils import (
diff -ruN a/pdm/pep517/scm.py b/pdm/pep517/scm.py
--- a/pdm/pep517/scm.py	2022-08-06 17:29:41.931385300 +0200
+++ b/pdm/pep517/scm.py	2022-08-23 17:45:23.391722696 +0200
@@ -14,8 +14,8 @@
 from pathlib import Path
 from typing import Any, Iterable, NamedTuple
 
-from pdm.pep517._vendor.packaging.version import LegacyVersion, Version
-from pdm.pep517._vendor.packaging.version import parse as parse_version
+from packaging.version import LegacyVersion, Version
+from packaging.version import parse as parse_version
 
 DEFAULT_TAG_REGEX = re.compile(
     r"^(?:[\w-]+-)?(?P<version>[vV]?\d+(?:\.\d+){0,2}[^\+]*)(?:\+.*)?$"
diff -ruN a/pdm/pep517/sdist.py b/pdm/pep517/sdist.py
--- a/pdm/pep517/sdist.py	2022-08-06 17:29:41.931385300 +0200
+++ b/pdm/pep517/sdist.py	2022-08-23 17:45:23.391722696 +0200
@@ -6,7 +6,8 @@
 from copy import copy
 from typing import Any, Iterator
 
-from pdm.pep517._vendor import tomli, tomli_w
+import tomli
+import tomli_w
 from pdm.pep517.base import Builder
 
 
diff -ruN a/pdm/pep517/utils.py b/pdm/pep517/utils.py
--- a/pdm/pep517/utils.py	2022-08-06 17:29:41.931385300 +0200
+++ b/pdm/pep517/utils.py	2022-08-23 17:45:23.391722696 +0200
@@ -11,10 +11,10 @@
 from pathlib import Path
 from typing import Callable, Generator, Iterable
 
-from pdm.pep517._vendor.packaging import tags
-from pdm.pep517._vendor.packaging.markers import Marker
-from pdm.pep517._vendor.packaging.requirements import InvalidRequirement, Requirement
-from pdm.pep517._vendor.packaging.version import InvalidVersion, Version
+from packaging import tags
+from packaging.markers import Marker
+from packaging.requirements import InvalidRequirement, Requirement
+from packaging.version import InvalidVersion, Version
 from pdm.pep517.exceptions import MetadataError
 from pdm.pep517.macosx_platform import calculate_macosx_platform_tag
 
diff -ruN a/pdm/pep517/validator.py b/pdm/pep517/validator.py
--- a/pdm/pep517/validator.py	2022-08-06 17:29:41.931385300 +0200
+++ b/pdm/pep517/validator.py	2022-08-23 17:45:23.391722696 +0200
@@ -1,6 +1,6 @@
 from typing import Mapping
 
-from pdm.pep517._vendor import cerberus
+import cerberus
 from pdm.pep517.exceptions import PEP621ValidationError
 
 README_RULE = [
diff -ruN a/pdm/pep517/wheel.py b/pdm/pep517/wheel.py
--- a/pdm/pep517/wheel.py	2022-08-06 17:29:41.931385300 +0200
+++ b/pdm/pep517/wheel.py	2022-08-23 17:45:23.391722696 +0200
@@ -19,8 +19,8 @@
 from typing import Any, BinaryIO, Generator, Mapping, NamedTuple, TextIO
 
 from pdm.pep517 import __version__
-from pdm.pep517._vendor.packaging import tags
-from pdm.pep517._vendor.packaging.specifiers import SpecifierSet
+from packaging import tags
+from packaging.specifiers import SpecifierSet
 from pdm.pep517.base import Builder
 from pdm.pep517.exceptions import BuildError, PDMWarning
 from pdm.pep517.utils import get_abi_tag, get_platform, show_warning
diff -ruN a/tests/test_metadata.py b/tests/test_metadata.py
--- a/tests/test_metadata.py	2022-08-06 17:29:41.935385500 +0200
+++ b/tests/test_metadata.py	2022-08-23 17:45:23.391722696 +0200
@@ -5,7 +5,7 @@
 
 import pytest
 
-from pdm.pep517._vendor import tomli
+import tomli
 from pdm.pep517.metadata import Metadata
 from tests import FIXTURES