(FWIW, IANAL, and I Am Not SIL, but I've spent 15 years as the font development lead in the Google Fonts team, so am responsible for the majority of OFL fonts published and know a lot about how it plays out - and have worked with the SIL OFL v1.1 in a professional context since it was being drafted.)
At the highest conceptual level, I see that the OFL exists to bridge between the worlds of type design and libre software, so it is bound to "feel non-DFSGish". The tallest nail sticking out is the sales restriction, and https://wiki.debian.org/DFSGLicenses#The_SIL_Open_Font_License says, > The following restriction on distributions, which is part of OFL, has been widely accepted by open source projects when it is applied to fonts: "1) Neither the Font Software nor any of its individual components, in Original or Modified Versions, may be sold by itself." The RFN nail also sticks out but is rarely discussed, but I think its fair to question it - imHo when we talk about 'the' license it is a bit muddling in a way, because there are really two concurrent flavors of the SIL Open Font License version 1.1, one with and one without any RFN(s) asserted in the copyright notice. (To Charles' point, the mere inclusion of the license term text about this doesn't surface this dual nature.) So, to Nicholas' original question, I think the answer is that it does FEEL that way, but it is DFSG compliant CLEARLY when there are no RFNs and BARELY when there are; and Soren nicely explained the practicalities of how its just 'over the line'. I seem to recall that the RFN terms were inspired both by the Bitstream Vera license made for GNOME's commission of those fonts ( https://dejavu-fonts.github.io/License.html) and early versions of the LPPL (eg https://www.latex-project.org/lppl/lppl-1-0/) and I believe packages under both licenses are in 'main' (e.g. ttf-bitstream-vera and fonts-dejavu - I'm guessing the Vera package uses the same packaging technique as Soren used for Adobe Source) and the principle #4 that Sune mentioned is there because such terms go back a long way in libre licensing.
