VL6 Standard Gold + KDE4 + KBasic binary professional installer = working
I just tested this and kbasic starts fine, however depending on how you install kbasic you may need to clean up .desktop files and move accordingly. Regardless, I just test running from terminal and it worked fine. The gpl/commercial dual-licensing is confusing to me, but since I just wanted to test the installation I don't really care.
Summary: It works in VL6+KDE4. Nothing special needs to be done to install the (professional) binary.
Hope this helps!