The "free dollars" version is community supported, unmaintained, and nearly two years out of date. But it does work
fairly reliably for some non-critical applications..
The paid version is fully supported by the lead developer of OCPN, provides access to a dedicated OpenCPN
for Android support forum, and is based on the current
OCPN code base. It is updated periodically for bug fixes and feature upgrades, including additional plugins, chart types, etc.