However, URP and the software artefacts necessary to speak it are evolved compatibly, so it generally works to make an external program use such files that don’t come from the targeted LO installation, but rather from a different source.

So, to make that work, some way of accessing a flatpak’s arbitrary data and code files from outside the flatpak would be necessary, and some mechanism by which the paths that unoinfo reports can be mapped from flatpak-internal to flatpak-external paths. However, in the case of flatpak, something like flatpak run -command=/app/libreoffice/program/unoinfo java isn’t useful to a program outside the LO flatpak sandbox, as the reported paths don’t exist outside that flatpak. This is done with the unoinfo helper executable (see desktop/README.md for details).

LO includes all these files, so one way of obtaining access to those files is to ask the LO installation that the external program wants to target about the location of those files. When external (C++ or Java) programs want to communicate with LO via the UNO Remote Protocol (URP), those programs need access to certain libraries (C++ dynamic libraries or Java jars, resp.) and helper data and code files (e.g., even in the case of Java jars, these reference native code that is implemented in helper native dynamic libraries see for details on all this).

Openoffice vs libreoffice 2017