This means Basecamp migrated from the first Rails release up to the edge one. So how come people say so frequently how hard is to update their applications from Rails 2.1 to Rails 2.2? And the answer is simple: plugins.
Rails Long Term Support
Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)
Prevents you from data breaches and liability risks