Please include the paragraph below anywhere you use the character:

The open source character of Captain Union, created by Don Smith, has been released to the Public Domain, and is available for use by anyone with only the following conditions: this paragraph must be included in any publication involving the character, in order that others may use this property as they wish, following the same rules as Public Domain properties. The main rule being that your version's story cannot be like the story of anyone else's version (meaning: you may not reference elements from the story you find the character in, because they belong to that story's author, and are not open source).