PCgen appears to be missing the Dervish Dance feat and I'd like to add it. I'm familiar with the homebrew files, but unsure how to add the bonus for that feat as I'm only proficient enough to copy and past the line in.
As CarlCravens said,
This isn't an oversight: All campaign source books and player guides files have to be added to the sources list manually.
Dervish Dance is in the Inner Sea World Guide file. Open your character, go to menu Sources -> Select Sources, Advanced tab, open the Paizo Publishing section and add the ISWG to your sources.