Can I Use GNU General Public License?
Software under the GPL may be run for all purposes, including commercial purposes and even as a tool for creating proprietary software, such as when using GPL-licensed compilers. Users or companies who distribute GPL-licensed works (e.g. software), may charge a fee for copies or give them free of charge.
Under the GPL, either static or dynamic linking requires the main program to be distributed under the GPL, with the result that linking a GPL-licensed library is incompatible (in licensing terms) with a proprietary program. Under the LGPL, only static linking requires the main program to be distributed under the LGPL.
Using GPL code in your software: the essentials - Clendons
Can I use GNU Affero General Public License?
The GNU General Public License permits making a modified version and letting the public access it on a server without ever releasing its source code to the public. The GNU Affero General Public License is designed specifically to ensure that, in such cases, the modified source code becomes available to the community.
GNU Affero General Public License
The GPL is a free software license, and therefore it permits people to use and even redistribute the software without being required to pay anyone a fee for doing so. You can charge people a fee to get a copy from you. You can't require people to pay you when they get a copy from someone else.
Frequently Asked Questions about the GNU Licenses
GNU packages need not be FSF-copyrighted; this is up to the author(s), generally at the time the package is dubbed GNU.
Copyright Papers (Information for Maintainers of GNU Software)