Never had a problem with that, but after updating to ArcGIS 10.3 I cannot load shapefiles from a read-only drive. The error message says:
Error opening feature class FDO error: -1 [nnn.shp] FDO error: -1 [nnn.shp]
After clicking OK the following warning occurs:
Could not add the specified data object to the map. FDO erro: -1 [nnn.shp]
Still I am able to open the shapefiles using other GIS tools. Probably ArcGIS 10.3 is trying to write a lock file into the folder. Everything worked fine in ArcGIS 10.0.