"Since I plan on making changes, incorporating some available patches and releasing this (*how ambitious of me *) I might as well do it right and plan for the worst."

Although the project has not been active for a long time, it is best if you contact the author and keep a record of the response. It is really incredibly rare and only in the most desperate situations that hackers fork code without the explicit permission of the original author; even in the case of a GPL type license which makes it easy to fork, people still do their best to get in touch with the original author.

If you do manage to contact the author, you may even arrange to take over the project from SourceForge.