Technically, making improvements to the program itself is not modding, it\'s more like opensource. Modding is usually extending a program through well defined points. I wouldn\'t normally quibble over words, but there is a distinction in how to implement either.
For mods, Schema has to build in extension points into the code. (That\'s the right way. The wrong way is what Minecraft did and have someone hack them in.) For improvements, the code needs to be open.
Personally, I don\'t think making the code open source is the right direction for Schema. It would have a good chance of killing any chance of it going commercial. If it doesn\'t go commercial, it will always be a pet project with a small following.
There are other choices. The model I would recommend is the one Linden Labs used with their Second Life client. They made the source code open to read, and would let other people create their own derivitives of it, as long as they signed up for a license key. (Their servers wouldn\'t respond to unlicensed clients.) More pertinently to your suggestions, they also let people submit suggested changes to the code base. It\'s not true open source where anyone can post changes, but controlled.
This approach would give Schema a nice \"force multiplier\" to his development. This project has grown past what one developer can support. These \"600 little improvements\" are what the community needs, but he can\'t do that sort of thing on his own. But, if he spent one less hour a day developing and instead used that hour to approve/reject community submissions, the project would advance a lot faster.