- Do you intend to keep the ownership for 'the future'? -- Apply your own style whenever you make changes and/or additions. Potentially, work through the module applying your style all over. (You will learn a lot more about the module in the process.)
- Do you think you will soon hand this module over to someone else? -- Follow the same style as the original author.
- Do you think the module is mature enough to not need any more significant development? -- Consider following the same style as the original author.
Everything went worng, just as foreseen.