Releasing a unique hack mostly using other people's stuff

[tamarian]

My $0.02 cents worth: It will depend on the original hacks. Check the copyright notice inside the code files. If there are no copyrights anywhere, then it is public domain, you can use it freely. Some licenses are GPL, which means you can also use them freely, as long as your hack is also GPL or GPL-compatible. Some copyright notices/licenses clearly state that you cannot distrubute, change or do anything with it without permission, in this case, ask the author if they don't mind.

It's always a good practice to ask the author, just in case and to avoid hard feelings