Last I heard both
FPSC and
DBPro now exist in "free" versions.
The limitation is that you're not allowed to sell anything you create using them, which you can do if you pay for a license.
As far as I can imagine you can use the free version to create something and then buy the license once you get far enough to release anything. Compared to other game engines etc. these products are very cheap so I would probably recommend paying for them right away just to avoid the advertisements of the "free" versions
"Why do programmers get Halloween and Christmas mixed up?" Because Oct(31) = Dec(25)