if you need the reference:

Posted Jul 28, 2004 13:58 UTC (Wed) by coriordan (guest, #7544)
In reply to: dual license model is "rms ok" by JoeBuck
Parent article: Choosing an open source license (NewsForge)

RMS says: ``I think it is acceptable to do what MySQL AB and TrollTech do: release under the GPL, but sell alternative licenses permitting proprietary extensions to their code. My understanding is that all the code they release is available as free software, which means they do not develop any proprietary softwre; that's why their practice is acceptable.''

Below that paragraph is: ``(Footnote: RMS added later: "I later learned that TrollTech does develop proprietary software. I apologize for having mentioned it erroneously.")''