diff --git a/classes/licenses.yaml b/classes/licenses.yaml
new file mode 100644
index 00000000..ea3f941d
--- /dev/null
+++ b/classes/licenses.yaml
@@ -0,0 +1,36 @@
+metaEnvironment:
+    PKG_LICENSE: "$(pkg_license)"
+
+privateEnvironment:
+    PKG_LICENSE_PATH: "$(pkg_license_paths)"
+
+buildVars: [PKG_LICENSE, PKG_LICENSE_PATH]
+buildScript: |
+    if [ -z ${PKG_LICENSE:-} ]; then
+        echo "PKG_LICENSE is missing!" 1>&2
+        exit 1
+    fi
+    mkdir -p .bob
+    if [[ ${PKG_LICENSE} == LicenseRef* ]]; then
+        ID=${PKG_LICENSE#LicenseRef-}
+        if [[ $ID =~ ^[A-Za-z0-9.\-]+$ ]]; then
+            mkdir -p .bob/licenses/$ID
+        else
+            echo "LicenseRef contains invalid characters: ${PKG_LICENSE}"
+            false
+        fi
+        while read -r lic; do
+            _path=""
+            _file=${lic}
+            if [[ ${lic} == *:* ]]; then
+                IFS=: read -r _path _file <<< ${lic}
+            fi
+            mkdir -p .bob/licenses/$ID/${_path:-}
+            cp $1/$_file .bob/licenses/$ID/${_path:-}
+        done <<< ${PKG_LICENSE_PATH}
+    else
+        echo "${PKG_LICENSE}" >> .bob/license
+    fi
+
+packageScript: |
+    cp -r $1/.bob .
diff --git a/config.yaml b/config.yaml
index ca8734ee..2ad7abd3 100644
--- a/config.yaml
+++ b/config.yaml
@@ -6,3 +6,4 @@ plugins:
     - vsenv
     - msbuild
     - config
+    - licenses
diff --git a/plugins/licenses.py b/plugins/licenses.py
new file mode 100644
index 00000000..0d60a1e3
--- /dev/null
+++ b/plugins/licenses.py
@@ -0,0 +1,83 @@
+# Defines the "License" recipe key that can be used to describe the package license.
+# If the package uses a vanilla license with a known spdx.id the license can be specified as:
+#
+# License: "GPL-3.0"
+#
+# and for custom licenses with a license file:
+#
+# License:
+#    Id: "devel.m4"
+#    Paths: "COPYING"
+#
+# The plugin also offers string functions to get these information back into the environment
+# to be used by the licenses class.
+
+# To enable the validation check of the license expression the license-expression module must be
+# installed. (e.g. 'pip install license-expression').
+
+from bob.errors import ParseError
+from bob.input import PluginState, PluginProperty
+from bob.tty import Warn
+import schema
+
+def expression_check(license):
+    try:
+        get_spdx_licensing().parse(license, validate=True, strict=True)
+    except ExpressionError as e:
+        # a raised exception message is not shown (?)
+        print(e)
+        return False
+    else:
+        return True
+
+def dummyCheck (license):
+    return True
+
+try:
+    from license_expression import get_spdx_licensing, ExpressionError
+except ImportError as e:
+    Warn ("Unable to import license_expression module. License expressions will not be checked!").warn()
+    license_check = dummyCheck
+else:
+    license_check = expression_check
+
+LICENSE_SHEMA = schema.Schema(schema.Or(str, schema.Schema({'Id' : str, 'Paths' : str})))
+
+class LicenseProperty(PluginProperty):
+    @staticmethod
+    def validate(data):
+        try:
+            lic = LICENSE_SHEMA.validate(data)
+        except schema.SchemaError as e:
+            print(e)
+            return False
+        if isinstance(lic, str):
+            return license_check(lic)
+        return True
+
+def pkgLicense(args, env, recipe, **kwargs):
+    lic = recipe.getPluginProperties().get('License').getValue()
+    if lic is not None:
+        if isinstance(lic, str):
+            return lic
+        else:
+            return "LicenseRef-"+lic.get('Id')
+    return "UNSET"
+    #raise ParseError(f"{recipe.getName()} has no LICENSE")
+
+def pkgLicensePaths(args, env, recipe, **kwargs):
+    lic = recipe.getPluginProperties().get('License').getValue()
+    if lic and isinstance(lic, dict):
+        return lic.get('Paths', "")
+    return ""
+
+manifest = {
+    'apiVersion' : "1.1",
+    'properties' : {
+        'License' : LicenseProperty,
+    },
+    'stringFunctions' : {
+        'pkg_license' : pkgLicense,
+        'pkg_license_paths' : pkgLicensePaths
+    }
+}
diff --git a/recipes/devel/m4.yaml b/recipes/devel/m4.yaml
index 3f54c836..dc5f0535 100644
--- a/recipes/devel/m4.yaml
+++ b/recipes/devel/m4.yaml
@@ -1,5 +1,7 @@
 inherit: [autotools, patch]
 
+License: "GPL-3.0"
+
 metaEnvironment:
     PKG_VERSION: "1.4.20"