Nicely done, it really is an absurd rule. When I graduated and moved in with my then significant other and two roommates in Medford, back in 2009, this is why I had to be kept off the lease. (As a side effect, this made me ineligible for a resident parking permit for the first few months, but the town had no problem giving me tickets for using a non-resident parking permit as a resident).
Nice; Colorado recently passed a statewide law that finally does away with a similar "U+2" rule in my own town of Fort Collins (as well as other such rules in Boulder and elsewhere). To progress!
Somerville historically had a zoning ordinance limiting housing units to at most four unrelated people:
any number of persons related by blood, marriage, adoption, or foster care agreement and up to three (3) additional unrelated persons living together as a single housekeeping unit
This is something I'd been unhappy about for years, and was enthusiastic about the "4 unrelated is outdated" campaign to change it in in 2018. So I'm very happy that after a request for a variance the city council instead ended up removing the restriction.
The actual change was in November, so I'm a bit late on this!
I also think there was an oversight, where the removal didn't include changing the text in section 7-153 which says "All schools shall be responsible for publicizing to their students the limitations of the city's zoning ordinance which limits occupancy to not more than four unrelated individuals." I've written to the city council to let them know.
I've also noticed that several school-affiliated sites still list this limitation:
Tufts: Off-Campus Housing and Zoning Ordinances.
Harvard: Harvard Housing Off Campus and Beckwith Circle.
I've written to Tufts and Harvard to let them know this has changed. I wasn't able to find this listed on any MIT or Lesley sites, and didn't check all the other Boston-area college websites.