There exists an additional download on the site that contains a web archive (WAR) that you can deploy to a servlet container such as Apache Tomcat. Before doing so though you need to start the database by running startDB.sh if on Linux or Mac OSX, or startDB.bat if on Windows. The download file name on the site starts with infinitypfm-web for example infinitypfm-web-0.3.5.tar.gz. Deployment of the archive depends on the web server you are using. For example, instructions for deploying to Tomcat 6 are here.
The URL for the web application will be http://192.168.1.100:8080/infinitypfm-rap/main with the ip address and port changing obviously for whatever your setup is using.
Note that the web client has a subset of the features of the desktop client. You can read about the specific differences here.
Infinity PFM launcher in the Applications -> Office menu on Ubuntu.