diff --git a/interfaces/IConsensusClient.sol b/interfaces/IConsensusClient.sol
index 4060702..32e8e97 100644
--- a/interfaces/IConsensusClient.sol
+++ b/interfaces/IConsensusClient.sol
@@ -1,9 +1,20 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {StateMachineHeight} from "./Message.sol";
 
-
 // The state commiment identifies a commiment to some intermediate state in the state machine.
 // This contains some metadata about the state machine like it's own timestamp at the time of this commitment.
 struct StateCommitment {
diff --git a/interfaces/IDispatcher.sol b/interfaces/IDispatcher.sol
index b6897d2..b037756 100644
--- a/interfaces/IDispatcher.sol
+++ b/interfaces/IDispatcher.sol
@@ -1,4 +1,16 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {PostRequest, StateMachineHeight} from "./Message.sol";
diff --git a/interfaces/IHandler.sol b/interfaces/IHandler.sol
index 5cc6851..691f64e 100644
--- a/interfaces/IHandler.sol
+++ b/interfaces/IHandler.sol
@@ -1,15 +1,20 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {IIsmpHost} from "./IIsmpHost.sol";
-import {
-	PostRequestMessage,
-	PostResponseMessage,
-	GetResponseMessage,
-	PostRequestTimeoutMessage,
-	PostResponseTimeoutMessage,
-	GetTimeoutMessage
-} from "./Message.sol";
+import {PostRequestMessage, PostResponseMessage, GetResponseMessage, PostRequestTimeoutMessage, PostResponseTimeoutMessage, GetTimeoutMessage} from "./Message.sol";
 
 /*
  * @title The Ismp Handler
diff --git a/interfaces/IIsmpHost.sol b/interfaces/IIsmpHost.sol
index 291ea4c..c839bf8 100644
--- a/interfaces/IIsmpHost.sol
+++ b/interfaces/IIsmpHost.sol
@@ -1,4 +1,16 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {StateCommitment, StateMachineHeight} from "./IConsensusClient.sol";
diff --git a/interfaces/IIsmpModule.sol b/interfaces/IIsmpModule.sol
index 50f115d..184d081 100644
--- a/interfaces/IIsmpModule.sol
+++ b/interfaces/IIsmpModule.sol
@@ -1,4 +1,16 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {PostRequest, PostResponse, GetResponse, GetRequest} from "./Message.sol";
diff --git a/interfaces/Message.sol b/interfaces/Message.sol
index 30de54c..a5ec627 100644
--- a/interfaces/Message.sol
+++ b/interfaces/Message.sol
@@ -1,4 +1,16 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {StorageValue} from "@polytope-labs/solidity-merkle-trees/src/Types.sol";
diff --git a/interfaces/StateMachine.sol b/interfaces/StateMachine.sol
index aedba25..41cdf07 100644
--- a/interfaces/StateMachine.sol
+++ b/interfaces/StateMachine.sol
@@ -1,4 +1,16 @@
-// SPDX-License-Identifier: UNLICENSED
+// Copyright (C) Polytope Labs Ltd.
+// SPDX-License-Identifier: Apache-2.0
+// 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 solidity ^0.8.17;
 
 import {Strings} from "@openzeppelin/contracts/utils/Strings.sol";