Aspell has undergone an extremely large number of changes since the previous Aspell/Pspell release. For one thing Pspell has been merged with Aspell so there in no longer two separate libraries you have to worry about.
Because of the massive changes between Aspell/Pspell and Aspell 0.50 you may want to clean out the old files before installing the the new Aspell. To do so do a `make uninstall' in the original Aspell and Pspell source directories.
The way dictionaries are handled has also changed. This includes a change in the naming conventions of both language names and dictionaries. Due to the language name change, your old personal dictionaries will not be recognized. However, you can import the old dictionaries by running the aspell-import script. This also means that dictionaries designed to work with older versions of Aspell are not likely to function correctly. Fortunately new dictionary packages are available for most languages. You can find them off of the Aspell home page at http://aspell.net.
The Pspell ABI is now part of Aspell except that the name of everything has changed due to the renaming of Pspell to Aspell. In particular please note the following name changes:
pspell -> aspell manager -> speller emulation -> enumeration master_word_list -> main_word_list
Please also note that the name of the language-tag option has changed to lang. However, for backward compatibility the language-tag option will still work.
However, you should also be able to build applications that require Pspell with the new Aspell as a backward compatibility header file is provided.
Due to a change in the way dictionaries are handled, scanning for .pwli files in order to find out which dictionaries are available will no longer work. This means that programs that relied on this technique may have problems finding dictionaries. Fortunately, GNU Aspell now provided a uniform way to list all installed dictionaries via the c API. See the file list-dicts.c in the examples/ directory for an example of how to do this. Unfortunately there isn't any simple way to find out which dictionaries are installed which will work with both the old Aspell/Pspell and the new GNU Aspell.