To be fair, I think the term "proprietary" as used here describes systems that are not fully and publicly documented. Baudot and RTTY have long been fully documented, so they are not proprietary. I doubt they ever were, as even when they were patented I suspect the air interface (the character sets and the way they're sent) was publicly documented. The only part of Winlink/Pactor that is proprietary by this definition is the Pactor 4 modem. But it is not the only proprietary air interface on the ham bands; the ABME codecs in DMR, D*Star and Fusion are also undocumented (and patented). You can buy a black box from SCS that does Pactor 4 and use it to monitor Winlink (or anything else using Pactor4). And you can buy a black box from DVSI that does ABME and use it to monitor digital voice. Both require appropriate "glue" hardware and software to form a complete monitoring system, the functions of which are not proprietary, i.e. they are openly documented. This includes the compression scheme in Winlink. Personally, I strongly dislike proprietary (ie., undocumented) air interfaces on the ham bands. But that ship has sailed. Were they to be banned now, not only Pactor4 would have to go, but also all three digital voice modes. There's no way to distinguish them legally. The best way to beat proprietary air interfaces on the ham bands is to beat them at their own game: produce something better and put it out as open source.