Installing a .deb file can be done via the commandline tool dpkg:
dpkg -i hiawatha_6.11_i386.deb
This works for both Debian and Ubuntu (which is a Debian clone).
Installing on other OS's is done via the source tarball:
tar -xzf hiawatha-6.11.tar.gz
Compiling from source requires several developer libraries to be installed. How this is done depends on what OS you are using. I'm not familiar with CentOS and Slackware (last time I used those is more then 5 years ago), so I can't help you with that. Use their support forums for help.