If you want to reverse engineer the DG4000 in order to "fix bugs" for yourself, that will be highly unlikely, especially that what it is described there as bugs are, in fact, in spec DC offset, or expected behavior from a DDS type of generator.
A DDS is different from an analog generator, it first lay down a waveform in memory, then it samples that waveform. Waveform frequency is achieved by sampling memory at different increments of addresses, so it can get into apparently weird behavior when slowly changing the frequency of a given waveform, especially for square waves or pulses.
I admit I didn't read the bugs topic very carefully, but they all looked to be expected behavior coming from a DDS architecture.