Aaron suggests that anyone interested in contributing to Mootools development should drop a note here. So here I am. :)
I've actually kept using 1.1.1 because of some bugs and performance issues introduced in 1.2. But I really want to take advantage of the 1.2 stuff, and seeing the forward momentum into 1.3, I'm excited to get involved. I'm interested in patching bugs in 1.2 and contributing 1.3. I'll start today by re-evaluting my projects in 1.2.1 vs. 1.1.1 and checking the bugs I encounter against the Lighthouse tickets. I know there was a severe performance degradation in 1.2 in drag-and-drop with multiple drop targets, due to a low-level change in how element boundaries were checked. I'm eager to see if that's been fixed, and if not, that may be my first contribution. :) Please let me know how else I can be of help.
