Include PEAR-components into a commercial/open-source project

Dear Developers of the PEAR-Classes, we are currently relaunching our little, nice project and would now like to include some of the great PEAR-classes. With this relaunch, we also provide to our customers a new system of paid support and a paid copyright removal. The source itself remains open and everyone can use the script. We aren't yet sure, if we will still provide free support for those who don't pay. Is it possible to use PEAR-classes in such a project? Thanks a lot for your time and your efforts! Regards, Philipp Boutellier