Seems a bit funny since just last September they blogged their mobile version and "no app required."
https://basecamp.com/1679267/announcements/10
One of the reasons I recall this is that I saved this particular e-mail newsletter at the time. I thought it of particular interest they dedicated resources on making a mobile browser performant version and had eschewed a mobile application approach. So what has changed or did they feel a deficiency in that version?