Try this:
class BWCUi(bpy.types.Panel):
bl_space_type = 'VIEW_3D'
bl_region_type = 'TOOLS'
bl_label = "Bone Weight Copy"
bl_context = "objectmode"
bl_category = "Steps" #or another tab-name
bpy.types.Scene.BWCInter = IntProperty(name="Interpolation",
description="Base Mesh subdivides (Higher interpolation -> Better matching weights)",
min=0,
max=10,
default=0)
bpy.types.Scene.BWCNamedBones = BoolProperty(name="Only Named Bones",
description="Copy only the bone related weight groups to Target (Skip all other weight groups)",
default=False)
bpy.types.Scene.BWCEmptyGroups = BoolProperty(name="Copy Empty Groups",
description="Create bone related weight groups in Target, even if they contain no vertices",
default=False)
and remove the the “def initSceneProperties”,
The bl_category was missing and putting properties on the scene has already changed very much more then a year ago, which I do not understand fully, but putting the body of the removed def just in the Panel,
you will get the buttons in the tab of the Panel (“Steps” if you do not change this name")