Is Pynagram stable?

Yes. You are unlikely to have your computer crash just by playing Pynagram. However, a small distinction is made between "stable" and "unstable" series.

Stable series have polished releases. Installers should work as expected, icons and descriptions will be properly done, etc. Unstable releases generally have rough edges and may not look great.

Releases with an even minor version number (i.e 'y' in x.y.z) are stable releases and those with odd minor version numbers are unstable. For example, the 0.4 series will have polished releases that have developed in the 0.3 unstable series.