The reason I had to install tealecho is the program told me it needed it. Maybe there are different versions out there. I think that tealecho came in as one of the programs in the file I downloaded. I don't care that much, since I don't think I'll be using isilo -- I was just trying it out. I use FBreader, mainly.

I don't think FBreader can specifically read isilo files, but those files can be converted to some format FBreader can read, I would assume.