The function for native support of dynamic resize is not complete or
necessarily correct. (It can't ever be really correct - see bugid 4446197).
Enlightenment can support dynamic resize. I don't believe OLWM or MWM can.

/*
 * Class: sun_awt_motif_MToolkit
 * Method: isDynamicLayoutSupportedNative
 * Signature: ()Z
 */
JNIEXPORT jboolean JNICALL
Java_sun_awt_motif_MToolkit_isDynamicLayoutSupportedNative(JNIEnv *env, jobject this)
{
    switch (awt_wm_getRunningWM()) {
      case KDE2_WM:
      case SAWFISH_WM:
        return JNI_TRUE;
      case CDE_WM:
      case ENLIGHTEN_WM:
        return JNI_FALSE;
      default:
        return JNI_FALSE;
    }
}