OpenMRS can only support up to three released versions at a time (the current release and then two versions back). The previous versions are kept in folders called 1.5.x or 1.6.x and only small bug fixes are applied to those branches. This makes those branches relatively stable and very similar to all releases in that minor version (e.g. 1.5.1 will be very similar to 1.5.9)
What does it mean to be End Of Life (EOL)?
Bugs are no longer backported to these versions
The core team will not be backporting and committing patches to that release's folder.
No longer supported by core developers
Bug reports for end of life versions will be answered with 'please upgrade to a supported version and confirm it is still an issue'. We will not be releasing new maintenance point releases in that line.