Everyone is welcome to join, regardless of talent or previous experience. We're always looking for new people to join, so don't be hesitant to join in the middle of the term or to quit and then rejoin again.
The attitude of the Student Software Group is much more relaxed than that of most other clubs and organizations at UW. The whole purpose of the group is to get students involved in stuff that they're interested in and not necessarily to actually complete anything (it sounds silly, but it's true). If you feel that you don't have the skills necessary, don't understand the algorithms, don't have the time to commit to anything, yet are still interested in the project being worked on, you are an ideal member of the Student Software Group. You have the most to gain by being part of the group, and you are not obligated to contribute any code, show up at any of the meetings, or participate in anything which you don't have the time for.
So to join, just send an e-mail to Ming-Yee Iu at my2iu@undergrad.math.uwaterloo.ca.
Remember, the Student Software Group exists because of and for its members. If you have any questions, comments, suggestions, ideas about directions of the group, or whatever, feel free to contact Ming at the above e-mail address.