We really would’ve loved to. But we do not have sufficient rights, let alone all the source code of OS 3.9. Many components you’ll get with 3.1.4 are re-implementations of 3.9 components. For example, the printer.device is "all new", but despite its version number, not based on the V44 printer.device from OS 3.9.
We did not have anything as backup for the OS 3.9 HDToolBox, so we used the old one and fixed (at least) its most obvious bugs.
