Regarding Genetica, I am pretty sure you are correct in your assumption. You will need the full version to make variations and changes to existing textures. For the price, I think that's too high for just our map texture needs, unless you're wealthy, then the cost might be insignificant. I more often find usable textures from existing photo sites, then altering them in PS/GIMP to get them in more tileable format.
Genetica is on my list of possible software to obtain, but sits very low on my list of software needs.