I should add that I volunteered to maintain this project, in exchange for free stuff from said organization (not money), before I knew what I was volunteering for (heh, lesson learned).

3 years (of occasional work, maybe 1-4 hours a week) later and I've got a layer on top that can interact with all of the slightly different data models of the four apps and I'm gradually replacing the legacy code with new code and migrating them all back into a single database/app.

Since I'm not working for money, I maintain sole ownership of the code, and I hope to eventually turn it into a passive income source, since it will be useful to other, similar organizations who have it even worse as far as their web applications go.