Hello,
The trunk version of wxFormBuilder does not currently build on MAC OS X. These patches fix compilation issues on Mac OS X (yosemite).
Sorry about making 2 patches instead of 1; due to externals it became hard to make a single patch.
Applying patches
patch for trunk
Also, note that wxFormBuilder will crash when using wxWidgets master, due to a bug with wxPropertyGridManager::SetPropertyAttributeAll
See http://trac.wxwidgets.org/ticket/16922
Applied to the trunk. Thank you for the patch!