A custom CMS is like getting a custom suit tailored, from scratch. When working with your trusted tailor, you know that when he has finished his work, your suit is going to fit perfectly. Using a free, open-sourced CMS is like buying a new suit, and then having it adjusted to fit your unique body. It still fits, and may look good, but it's just not the same. The pockets might be a little low, shoulders a little tight, fabric may be bulging on the waist. Custom CMS vs the free platform.