Oh, yes. This appears to be true. Tesannwyn.esp is renamed to island.esp. This should be easy to figure out, but I´ll put more effort into documentation next time.
However the readme clearly tells you about the MyGUI thing.
Windows:
"everything in ./resources/mygui goes into C:/Program Files/OpenMW 0.36.1/resources/mygui"
Linux:
"everything in ./resources/mygui goes into ~/.local/share/openmw/resources/mygui"
Okay, so i have Pelagiad.ttf and openmw_font.xml inside ~/.local/share/openmw/resources/mygui and the fonts are still not showing up.
Were is the mistake?
EDIT: Turns out putting the font related files under ~/.local/share/openmw/resources/mygui doesnt work, if you want fonts under linux, you have to put them in /usr/share/openmw/resources/mygui.