I'm working on a "for fun" project together with some online friends. We do not intend to make money on it or become famous or anything. We're just doing it because we're like-minded individuals and we believe that together we can create something cool and improve our skills in the process.
We all have many other things going on in our lives, such as school, work, parenting, and so on. Because of that the progress slows down from time to time. Since it's a free project that's not meant to be too serious, I don't think it's right for me to get angry about occasional periods of inactivity.
But still, I feel like certain members of the team could use some discipline. I know that they are indeed quite busy dealing with other responsibilities, but I'm certain that if they tried a little harder they would be able to do more without it seriously affecting their everyday lives.
How can I bring up this matter in a tactful manner (either by making a statement for everyone to see or discussing the issue with my teammates individually)?