Legal aspects of use of free libraries and cms for development?

Any legal collapse no. You are not just creating a program, and a composite work, which includes programs of other authors. In your case the composite work burdened with the additional conditions imposed by open source license.
\r
Personally, I would recommend to put in the source for the original license and pay this to the attention of the client. In fact, the text of the Treaty it is necessary to distinguish that such part of the works is transferred the exclusive right, and such right of reproduction and other rights that provides a specific license. The license itself not worth mentioning, as well as to bring out her quote.
\r
After that, the lawyers and accounting client slowly go mad but you'll be clean before domestic law and open licenses.

Depends on the license used programs. If LGPL, then just dynamically lenquete, and in the program folder a file with the LGPL. If BSD or MIT, then you can even assign the like.

The easiest way if you don't want to understand the compatibility of the licenses among themselves and our legislation is to "force" the client to download jQuery and WordPress, and to tell him only your code and your license with instructions on integration. For our "bodies" that should be enough.

Unable to do the same as in Quake, they just pointed out that the rights to the game belong to ID, and in some parts of the engine (such as a ZIP algorithm) — their developers.