You may use the did-io project under the terms of the BSD License.

You are free to use this project in commercial projects as long as the
copyright header is left intact.

If you are a commercial entity and use this set of libraries in your
commercial software then reasonable payment to Digital Bazaar, if you can
afford it, is not required but is expected and would be appreciated. If this
library saves you time, then it's saving you money. We are attempting to strike
a balance between helping the development community while not being taken
advantage of by lucrative commercial entities for our efforts.

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