Hi,
Thanks for your question. I understand your situation. There is no short term plan to support 3rd party hardware units like Velleman's, however I will consider it for in the future.
Meanwhile, perhaps the older type RS-232 DMX output unit could be a solution for you; they are regularly being offered second-hand by VisualDMX users who upgrade to the USB device. If you'd like you can email me directly so I can see if can put you in contact with a few of them.
Best regards,