LGPL is designed for libraries. Static or dynamic linking to LGPL code is allowed without enforcing copy-left. That means that the derivative work can even be a proprietary software. However, if you change the library code itself, you modification has to be released under LGPL. Since version 3 LGPL is compatible with GPL, which means that the modifications could be released under GPLv3 too.
In case of CMS, all these doesn't matter in practice. CMS is not a self-contained isolated library and except of very simple projects, a web application build on top of it will require changes in the CMS code. So commonly, there would be the same copy-left enforcement in place as in case of the GPL. There is also no difference between GPL and LGPL with respect to the server deployment. Both licenses do not see that as distribution, so the deployed code, whatever type of changes it contains, can remain secret. That's why my recommendation was GPLv3, as in this case there is no way to get anything extra from LGPL anyway. I guess the key difference is in the licenses compatibility. Under LGPLv3 you can include all non copy-left free software (BSD, MIT, MPL 2.0, Apache 2.0) but not the code under the GPL (you would have to release the combination under GPLv3, for details see the compatibility matrix [1]). With GPLv3 it's simpler as more licenses are compatible (see the full list [2]), including GPLv2 as long as the phrase "either version 2 of the License, or (at your option) any later version" is present in the copyright notice. For more arguments in the GPL vs LGPL case see [3]. [1] http://www.gnu.org/licenses/gpl-faq.html#AllCompatibility [2] http://www.gnu.org/licenses/license-list.html#GPLCompatibleLicenses [3] http://www.gnu.org/licenses/why-not-lgpl.html
