When there are multiple parameter files for the same encoding, only one can be installed at a time. The installation script detects that and warns the user. The user is able to force the installation with -f. Future releases might add alternative naming scheme.
The list of installed parameter files is saved under your home folder, in a dot file. Usually only the system administrator will be able to install parameter files, and therefore the dot file will be up to date with his actions. If multiple users can install parameter files each one will have a dot file, and the information will not be coherent.
Although more architectures are available at Tree Tagger home page, at the moment I just support linux (both 32 and 64 bits) and Mac OS X on Intel hardware. Future versions might support further architectures and operating systems. Patches are welcome.
The basic Tree Tagger tarballs include a lot of scripts that does not work without the respective parameter files. At the moment those scripts are installed anyway, but will not work if the respective parameter file is not available.