I have a client who requires a content management system that can be installed on their host manually by them in a sub folder or on other hosts for their customers as needed

It needs to be like ImpressPages CMS with the creation and editing of pages being done dynamically dragging and dropping content cutting and pasting text and images etc to change the layout and content of the pages and then saving to update the live pages, also needs easy addition of modules/plugins such as a gallery, paypal integration stuff like that in future

ImpressPages CMS is perfect but for one problem, it is built to only work on php 5.3 and above and my client has php 5.2 and cannot change to php 5.3 as it messes up many other scripts and sites they have on that host

Can anyone suggest a free content management system similar to the one mentioned above that will work on php 5.2 or below

Thanks in advance