NeoOffice is a fork of the well known office suite OpenOffice.org customised for Mac OS X. When it was created there was no Mac version of OpenOffice and even when I started three years ago, the Mac support for OpenOffice was very poor. There have always been licence anomalies between the two versions—OpenOffice is LGPL and requires a copyright assignment for contributions to the main code. NeoOffice were not prepared to do this so their code is licensed under full GPL and is not retrofitted.
Up until now, it has always been free at source with a recommendation/plea for donations to support the work, which I have done at least once. Now, since Version 3.2, the “donation” is mandatory—you can’t download the code unless you have donated at least $10US within the last year.
Times have changed—it now requires Mac OS X 10.5+ and Intel hardware which must kill off a sizeable proportion of their customer base. Also OpenOffice and now LibreOffice are much more capable. Finally, if you must pay for it, the iWorks components are much more affordable and also offer cross format capabilities.