I'm using the mac version of OpenRCT and it's working just fine, thanks for your great work!
However, I also downloaded the RCT1 files, using the appropriate Game-ID 285310 and Depot ID 285312 (German version) in Steam console.
But OpenRCT won't accept them - everytime I try to set the path for the RCT1 files using OpenRCTs option menu, the prompt "Bitte wählen Sie ein valides RCT1-Verzeichnis" (I'm guessing "please specify a valid RCT1 directory" or similar in english) is displayed. Why won't it accept the RCT1 directory? All the files are there.
EDIT: I now also tried to use the english depot 285311 - it won't accept that, either.
EDIT 2: I managed to do the trick myself - by editing the config.ini in the OpenRCT directory and manually putting the RCT1 path in there. Now, open RCT shows the RCT1 content - still it's rather strange that it wouldn't let me pick the directory using the options menu!