The license does not seem to be stated for the Constant Contact PHP Library at:
I'm assuming it's open source, but need to know the specific license terms being referenced.
All of our sample codes are currently under the Apache License, Version 2.0. Thank you for pointing this out as we do need to add this information to the libraries. I hope this answers your question, please let me know if you have any others.
While you're updating those, it might be worthwhile to take a look at Apache License Version 3.0. My understanding is that the new license allows more streamlined license citation which does not require the license be placed in each individual file. Just something helpful for you guys.