Now I see the package too. And I see also that Lazarus is mentioned in the readme.txt. Too much information for an old man...
I cloned Bernd's git repository and was able to compile and install the package with Laz 2.04 / fpc 3.0.4, Laz trunk/fpc 3.0.4 and Laz trunk/fpc trunk successfully without the error message that you report. If you have an older version of the package on your disk there is maybe a unit version conflict: in the package editor use "More" > "Recompile clean", or, in the IDE menu, go to "Tools" > "Configure Build Lazarus", check "Clean all" and "Switch after building to automatically" and click "Build".