I've added depth testing and blend modes to the project and plugin. For those who haven't been keeping track, this is a Quad Warping plugin (and Xcode project) that is somewhat similar to Kineme GLQuad, save that it's QCPlugin (eg., standard API, that can be used in App Store applications), and with supplied, immediately compilable code that can serve as a starting point for other types of GL renderers.
If you already have this loaded, feel free to upgrade; it will not break any previously made compositions, it will simply give you new options for blending and depth testing.
It also has a few other unique features, like global translation and rotation controls. This can also be used like a regular Sprite. One could perhaps augment the project to only render the Quad when an input string matches another file (idle idea, not implemented), to serve as a lock out for your apps.
This supersedes previous releases. This has replace, over, add and alpha modes, as present in GL Tools (and/or Alpha Blend). This plugin doesn't need AlphaBlend.plugin to achieve alpha blending.
Thanks @ Anton Marini a.k.a. Vade, and Chris Wright for clarifications about depth testing and blend modes, but for not spoon feeding at the same time :-)