There are a number of variations on the clone (not going to validate or help by linking). The variation that has that notice on the PCB is complying with one of the terms of our open source license agreement:
https://github.com/T3P3/Duet/blob/master/LICENSE
Specifically:
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a. Attribution:
Any reproductions or modifications of the DuetWifi hardware must contain the following attribution on the silkscreen or packaging:
"Based on the DuetWifi by Think3dPrint3d and Esher3d, see www.duet3d.com for the original DuetWifi information. This reproduction/modification is not endorsed or supported in any way by Think3dPrint3d or Escher3d".
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The other clones do not comply with this term as they do not have the disclaimer. I have not personally checked any of the clones for correct component sourcing, assembly, PCB specification etc, buyer beware.
On the wider point about cloning this is a complex discussion. My start point is that @AdrianBowyer opensourced the RepRap: if he had not done that I think the 3d printing/additive manufacturing landscape would be totally different now. Arguably many of the companies and individuals who participate in using and improving 3dprinting would not be involved. RepRap was a paradigm shift that lowered the barrier to entry for everybody, and everyone involved benefited, and continue to benefit from that. The benefit that everyone (including us) gets from being part of, contributing to, an opensource ecosystem is huge. That said the development of the Duet can only continue at the level and form that it does with an element of commercial viability.
So what to do to continue to enable Duet and RRF development?
- Encourage people to buy a board from us or our official resellers.
- Report cloners to AliExpress or other retailers if the clones do not adhere to the terms of the license agreement.
- Continue to support this community by helping out on the forum, with beta testing, by contributing to firmware development or documentation as you can.
- Continue to blog, vlog, tweet, post, Instagram, etc about the awesome printers, CNC machines etc you are building with Duet.