This is the first time I see this map. I will definitely look into it.
The only official topo maps I know of are the ones produced in M1:5000 in the 50s to 70s and the M1:10000 produced in the 70s-80s. They're sold in a raster format by the sheet, so are completely useless to you.
On the toponyms part though, there's the official registry of toponyms that is openly accessible but not open-data. You can download it in its entirety thereby breaking copyright law:
Here's a preview of a search for "градище": https://i.imgur.com/7NPFoPz.png
Note the EU funds info box and annoyingly the copyright label below it.
Thank you a lot, that helps.
> Here's a preview of a search for "градище":https://i.imgur.com/7NPFoPz.png
That helps even more, thank you again!
I'm not doing this for any monetary gains and most probably the data/project will only be accessed by a handful of people really interested in this sort of stuff, so hopefully no-one will come after me :)
[1] http://web.uni-plovdiv.bg/vedrin/#section2
I was curious if it be possible to somehow integrate the data from there on a geo-referenced map, maybe there are some instructions on that page pertaining to that but unfortunately I do not know Bulgarian.
I'm one of your neighbours from the North (I'm Romanian) and one of my side-projects involves geo-locating some toponyms that I find interesting (like toponyms indicating the names of some fortifications, for example, which would be gradishte in Bulgarian if I'm not mistaken). For the territory of Romania I managed to do that by integrating some Romanian military topographic maps with OpenLayers, I was thinking of extending my project to the entire Balkan area (that's why integrating those topographic maps of Bulgaria with something like OpenLayers or Leaflet would help me immensely).