The open letter focuses on concerns about the process so far, and not about specific naming choices. Affiliates and individuals that have signed have a diversity of views on specific names, but all are committed to a better, more community-driven process.
You should also note there is currently a branding survey that runs until July 7. There is concern that the consultation process and options on the survey do not adequately reflect community sentiment, given the effect name changes for the foundation and movement would have.
Additionally, it has been announced that there will be a WMF board meeting scheduled in July to discuss the branding issue, so it is important to express your views now.
Community Open Letter on Renaming (COLOR) on meta: