This page lists the small amount of code from the L3DT source that I've released over the years in response to user requests.
L3DT uses a number of free libraries and bits of code to do some dirty-work, including loading and saving images, various user-interface things, and the odd bit of encryption. See the list of libraries used by L3DT for links to the relevant projects.
I will consider requests for code to improve compatibility with other programs, and also for fairly-simple 'how did you do x?' problems. Please address such queries to aaron@bundysoft.com.