The tone of this comment is quite different from the text of the open letter to which you refer. Specifically this section. I don't have any personal knowledge either way, but this stood out to me.
> As it was revealed by Roman @rtsisyk it wasn't unusual for the Shareholders to use project's donations as their own money e.g. Alexander @biodranik paid for his personal holiday trip expenses this way. At the same time all other contributors were consistently denied any access to any financial information (even to the totals of money donated/spent). (It's fine for developers to be reimbursed for their hard work, but it should be done in a fair, transparent and accountable way.)
How do you square this with Organic Maps being organised as a for-profit entity?
In fact, nowadays there are many more closed parts in OM's map generator - many OM's bigger new features like hiking, cycling and bus routes depend on closed source improvements to the map generator. And some binary files required to build the app (e.g. packed_polygons.bin) are nowadays distributed under a custom non-FOSS data license. I.e. nowadays its basically impossible to fork OM as is with all its features - and the "right to fork" is a cornerstone of FOSS.
Also ref to: https://isitreallyfoss.com/projects/organic-maps/