
If you worry about copyright you might consider this Software BSD-Licensed.
If you are still worried, you might consider it GPL1/2/3 compatible.
But don't worry. If you need something formal:
The code is available under the Apache License, Version 2.0.

Boilerplate for Apache License 2.0:

Copyright various contributors to huBarcode, later pyStrich.
Main contributions are from HuDoRa from at least 2007 to 2013
Contributions since 2015 are from Method B Ltd

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.