All I want to know is what licensing allows me, the program author, to keep "author credits"(so no one can rip me off), and make all software created from this program to remain free (like Ruby License)
There are several permissive licenses which allow other people to do practically anything they want as long as they retain your original copyright notice. A few examples:
- MIT license
- BSD license family
- Apache license
But these licenses allow to relicense the software under a non-free license. If you want to ensure that your work remains free, you should use a strong copyleft license like the GNU Public License or the Mozilla Public License.