If you have a change, new problem, fix, added solution, etc. Feel free to send a pull request (against "develop" branch, but no worries if you do it against "master").
Try to keep the formatting as close as possible to some of the nicer problems (the early sections are most cleaned up). The problems come from OPL and the quality varies, and some of the problems are still a mess. I'd like to make them all reasonably simple and consistent in formatting and wording, and I'd like to make the code readable and easy to modify (currently it is quite messy in places).
One change I've made is that there are no labeled parts "a),b),c)". The problem with that is that for example Edfinity labels the inputs for the students by letters, and if a part has more than one input, this can easily get confusing. Since we're filling in the answer directly into the problem, there is no need to refer to parts anywhere unlike in traditional homework which is generally "filled out" on a piece of paper that's distinct from the problem. Best to keep the number of random labels flying around to a minimum.
One thing that would be good to add is as many solutions with explanations as possible. Early sections, being most used, are perhaps more of a priority.
There are also quite a few sections where there really aren't enough questions. I'm trying to go for about 10ish questions per hour of lecture, although this depends on how hard the questions are. It is always possible for an instructor to just remove problems from their homework, so having more problems (as long as it's not excessive) is not so much of an issue.
If you have some changes that are "noncontrovertial" in the sense they are fixes, and some that are suggestions that might need more work or review, it might be best to split them into several pull requests.
The license is the same as the OPL (because most problems came from there originally). That CC-NC-SA license. See LICENSE.md. So by submitting a pull request you are OK with your change being under this license.