Personally, I think if the original author can't be contacted for permission, then his code shouldn't be used - even if you give credit. If you desperately need the functionality of the old hack, then I feel you should write it again from scratch.
RC1 just came out a few days ago. There is no way that anybody has had time to say an original author can't be found or isn't going to release their work yet. People go on vacations for longer than a week or two. People change email addresses and don't update their profiles. Just cause you can't contact William Shakespeare, it doesn't give you the right to take his works, change the dates and maybe a name or two and re-release his plays
But, that's just my personal thoughts on that matter.