AFAIK, by default libraries created and shared by forum members are licensed under creative commons CC BY 3.0 license:
Creative Commons — Attribution 3.0 Unported — CC BY 3.0
Developers can choose a different license if they desire.
About selling the source code.
1) you, in any case, keep the rights as the original author of your software; they can't buy this (and you can't sell it)
2) you can sell the source (for their convenience; e.g. they could decide to hire someone else to manage the project) but this doesn't imply that you have
to sell exclusive rights on the code itself (or the project, for that matter)
3) since your project is made up of your code plus several third-party libraries, you should specify it and sell just your code (listing the third-party libs so they can try to acquire rights on them too, if they like)
4) take in account the app name (sell it or keep it at your own discretion)
It could be wise to ask for a legal opinion prior to set up a new agreement.