Yes, within limits.
If you have made good changes to it, so it is unique, then provided you give credit to the originator, you are at liberty to write an article about it and post it for moderation. If it passes that (and that isn't guaranteed - look at existing articles to get an idea what is expected) then it is freely available for download, just like the original program you started with.
Have a look here:
http://www.codeproject.com/script/Articles/Submit.aspx[
^] paying attention to the links in the top right.