LaTeX

The Open Logic project uses the typesetting system LaTeX. If you're the type of person who would teach an intermediate/advanced formal logic course, you probably know and use it already. But if you're checking OLP out because you think a make-your-own-adventure open source textbook is a cool idea, here are some links for finding out about it:

• The LaTeX Project
• LaTeX for Philosophers
• LaTeX for Logicians

LaTeX is free, runs on basically every type of computer, and is open source itself. The system it's based on, TeX, was designed specifically for mathematical typesetting.