Looks like there were major backward-incompatible interface changes to the public libdevhelp-1.0 between the different devhelp releases (I'm looking at 0.23 compared to 0.21) but the SONAME remained the same. If I upgrade the lib, that instantly breaks everything compiled against the old one and also makes sources that expect the old stuff no-longer-compileable. The library is built using libtool, so you can use the standard -version-info flag to indicate what types of changes are made in each release, and the SONAME and dyld version flags will be set automatically and correctly for the local OS.