2009.08.21 16:27 "Re: [Tiff] Libtiff 3.9.0 Released", by Bob Friesenhahn
In particular, note that 3.9.0beta was not ABI compatible with 3.8.2, but the changes introduced that broke compatibility were corrected in the 3.9 branch subsequently.
Also of note is that due to libtiff 3.X.X not using proper shared library naming conventions, the name of the shared library produced from 3.9.0 is the same as 3.9.0beta. This is a problem for any system which is already using 3.9.0beta since any dependent libraries/applications will need to be recompiled.
Starting with libtiff 4.0.0, libtiff will be using proper ELF versioning and will not be basing its shared library numbering directly on the libtiff version number.
OS distributions are free to apply their own shared library versioning rules in the mean time.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/