The nice thing about licences is that there are so many to choose from - the downside of licences is that there are so many to choose from!
IMINWLO (In My In No Way Legal Opinion!), you should get a real lawyer (i.e., not one of us non-lawyers on the list or elsewhere) to translate the available licences for you to digest. They have various uses and pitfalls, with features that prevent or enable other commerical entities to use your code (which you may/may not want to happen) and permit or restrict other noncommercial uses. In addition to GPL, another popular type of licence is Apache. FSF (the Free Software Foundation) is also a good place to look for pointers.
You may also have the choice of applying more than one licence at a time, letting the user choose which is applicable to them. You may even be able to add more licences over time, but I don't think you can recind licences for already distributed code (but may be able to change them for new versions).
Some licences (like most of the GPL variety) have a requirement that any modifications to source code be made available. There are usually (notice that I'm using 'weasel-words' to prevent being tagged with giving legal advice that I'm not legally competent or licenced to give :-) ways for you to permit open use by the community while still reserving commercial use to more restrictive licencing - if you so choose.
The bottom line is - get a lawyer who is working for your best interests to help determine how you want to licence your property, it will cost you less in lawyer fees (the only ones who really make money from most licences!) in the long run. Some licences have more 'overhead' to maintain than others, which might be a burden to your company (something that I really don't want to see!).