How to license a small app so people can use it freely?

[Fuzz13]

I have been working on a small program that checks a users routers IP address and sends an email when the returned address is different after the previous scan. I would like to make the program available for free to users and more then likely I would like it to be open source so others can modify it for their needs. I looked into SourceForge which I think is where I will go with it but it asks me to identify the programs licensing information. I have begun to read up on GNU but it is all very overwhelming right now. For something this small can someone make some recommendations on what type of licensing I should look into? Does it cost to license your program etc. Again I don't want to charge for it, I just want credit.

Thanks for any help provided.

[JKing]

GNU General Public License is the way to go.

This page explains it pretty well GNU GPL

[Fuzz13]

Thanks JKing I think that solved it. I added the little information about it being licensed under GNU GPL and will be uploading it to sourceforge now.