In the previously referenced thread, Wim (of DisplayLink) alludes to the problem you cite by mentioning this is all somewhat complicated because (among other issues) "the DL-3000 supports content protection."
This is indeed true. However, it is "possible" to allow open access to the none content protection sensitive parts of the protocol without compromising the devices security. I would be more than happy to write the open source drivers free of charge but I would need access to documentation that I no longer have access to, and possibly an extremely small level of cooperation from the firmware team, whom I know well.
Andy F