diff --git a/include/mgos.h b/include/mgos.h
index 8c4e194..2f9fbf9 100644
--- a/include/mgos.h
+++ b/include/mgos.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #ifndef __MGOS_H
 #define __MGOS_H
 
diff --git a/include/mgos_htu21df.h b/include/mgos_htu21df.h
index aeb21c9..281dd07 100644
--- a/include/mgos_htu21df.h
+++ b/include/mgos_htu21df.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/include/mgos_mcp9808.h b/include/mgos_mcp9808.h
index af0cd4c..2353b64 100644
--- a/include/mgos_mcp9808.h
+++ b/include/mgos_mcp9808.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/include/mgos_mock.h b/include/mgos_mock.h
index 5a633f0..8286082 100644
--- a/include/mgos_mock.h
+++ b/include/mgos_mock.h
@@ -1,8 +1,24 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Some functions mocked from MGOS, so we can run unit tests standalone.
+
 #ifndef __MGOS_MOCK_H
 #define __MGOS_MOCK_H
 
-/* Some functions mocked from MGOS, so we can run unit tests standalone.
- */
 
 #include "mgos.h"
 #include <time.h>
diff --git a/include/mgos_sht31.h b/include/mgos_sht31.h
index fe73cf5..edf8756 100644
--- a/include/mgos_sht31.h
+++ b/include/mgos_sht31.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/include/mgos_si7021.h b/include/mgos_si7021.h
index ea8ec39..4d9525c 100644
--- a/include/mgos_si7021.h
+++ b/include/mgos_si7021.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/src/main.c b/src/main.c
index 719c2ec..ab6acd5 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #include "mgos.h"
 #include "mgos_i2c.h"
 #include "mgos_sht31.h"
diff --git a/src/mgos_htu21df_internal.h b/src/mgos_htu21df_internal.h
index 8ee22ab..f6bd6b2 100644
--- a/src/mgos_htu21df_internal.h
+++ b/src/mgos_htu21df_internal.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/src/mgos_i2c.c b/src/mgos_i2c.c
index ad976c7..c22581d 100644
--- a/src/mgos_i2c.c
+++ b/src/mgos_i2c.c
@@ -1,3 +1,23 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Pim 2018-04-03: This is a Linux implementation of the mgos_i2c interface
+// which is useful to develop drivers directly on Linux. For Ubuntu/Debian,
+// make sure to install package 'libi2c-dev'.
+
 #include "mgos_i2c.h"
 #include <sys/types.h>
 #include <sys/stat.h>
diff --git a/src/mgos_mcp9808_internal.h b/src/mgos_mcp9808_internal.h
index ffc2057..4f5665c 100644
--- a/src/mgos_mcp9808_internal.h
+++ b/src/mgos_mcp9808_internal.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/src/mgos_mock.c b/src/mgos_mock.c
index 0a2dd8f..958dc14 100644
--- a/src/mgos_mock.c
+++ b/src/mgos_mock.c
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 /* Some functions mocked from MGOS, so we can run unit tests standalone.
  */
 
diff --git a/src/mgos_sht31_internal.h b/src/mgos_sht31_internal.h
index 7340dad..87585dd 100644
--- a/src/mgos_sht31_internal.h
+++ b/src/mgos_sht31_internal.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"
diff --git a/src/mgos_si7021_internal.h b/src/mgos_si7021_internal.h
index 7518f2d..11c5a07 100644
--- a/src/mgos_si7021_internal.h
+++ b/src/mgos_si7021_internal.h
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
 #include "mgos.h"