Using Emma is the Windows-only step that we are getting worked up about. If Jolla documents and supports a Linux-based alternative, then there is no problem, however James Noori says that Emma is required. This means Windows is required: early experiments with Wine are not encouraging. This is not speculation: read James' comments on the Jolla blog again if you think that it is.

What we don't know is the level at which Sony enforces the requirement for Emma. If they have simply asked Jolla not to support/document a pure Linux method, a community-supported Linux method will still work and things are still kind-of OK. OTOH they may have required Jolla to somehow add an extra level of signing and/or key verification to the official SFOS X image so that it won't be installable without Emma. That would be seen as an unethical move, and probably as an open invitation to crack the security and find a way around it (I don't have the expertise, but other people who hang out around here probably do).

We will have to wait until the official release to find out what the situation really is of course, but like I said I'm glad that I don't have James' job.