From the Wiktionary definition of software:
Encoded computer instructions, usually modifiable (unless stored in some form of unalterable memory such as ROM).
So yes, scripts obviously classify as software.
Now, if the only difference to you between GPL and CC-0 is the one you described, then you have a lot to learn.
In short, GPL used indeed to be the standard. It is not really the standard anymore, just one of the most common choices. MIT is also a very common choice. These two licenses are very different in what they allow, with MIT one of the most permissive and GPL one of the most restrictive. Apache 2.0 is also a common choice (see some recommendations here: http://choosealicense.com/).
For short scripts, GPL is generally not recommended (even by the FSF):
What if the work is not very long? (#WhatIfWorkIsShort)
If a whole software package contains very little code—less than 300 lines is the benchmark we use—you may as well use a lax permissive license for it, rather than a copyleft license like the GNU GPL. (Unless, that is, the code is specially important.) We recommend the Apache License 2.0 for such cases.
My preference for very short scripts goes to CC-0 because I want people to be able to reuse them in every way they want, without needing to attribute me. If this is also what you want, then go ahead and apply CC-0 to your work as detailed here: https://creativecommons.org/choose/zero/