Apophysis is a great tool for working with flame fractals. It is a free program and is not as polished or full featured as Ultra Fractal but I have found it very useful for flame fractals. You can create flame fractals and manipulate the color palettes although the interface is quite a bit different from Ultra Fractal.

One feature I like is the ability to build a color palette from an image file. That is something Ultra Fractal can't do. Luckily you can save the color palettes in an Ultra Fractal format. Sometimes I open an Apophysis color palette in Ultra Fractal because it was easier to set up in Apophysis. Sometimes I do the opposite.

There are two development groups working on Apophysis taking it two different directions. I've done my work with version 2.09. The other version is 7.x. I haven't found anything added to version 7.x that is useful to me yet. Beware that flames created with version 7.x may not look the same on version 2.x and vice versa.

You can obtain the v7.x software of Apophysis at sourceforge.net/projects/apophysis7x/ .