This bot is operated by Pintoch. As no request for bot approval has been submitted yet, its edits are performed by its owner.
It can update the participants list of your WikiProject (but will not do so unless it is told so). The update consists in moving inactive participants listed in the "active list" to the "inactive list" of your WikiProject. You can define what an "inactive participant" is. It supports both lists and tables.
For instance, MemberBot can mark participants as inactive when:
You choose what is relevant for your project.
It can also sort the two lists of members (active and inactive) if it is told so. And it can move inactive users who are actually active again to the list of active users.
Simply go to its talk page and fill the form about your WikiProject.
Note that when the changes are large, the diff algorithm outputs a diff that does not really reflect the activity of the bot. Check the page before and after if the diff looks suspicious.
MemberBot is written in Python, using pywikibot. It has an additional level of cache, so that it makes as few requests to the database as possible. The cache is refreshed in an adaptive manner: if we have seen one month ago that an user has made a contribution to the WikiProject two months ago and the threshold of the project is one year, then we don't look for more contributions because the user will stay in the active list anyway. Similarly, if we have seen that some user is not active on Wikipedia for a very long time, then we don't update him frequently as it's less likely that he starts editing again.
My code is available on github.