Our current expense policy includes

costs of server hosting/rental/colocation
costs related to our [currently annual] Osmocom developer conference (venue, catering, travel expenses)
hardware/equipment (BTSs, SDRs, …) for known/active Osmocom developers

Whenever travel expenses are covered, we're only covering

economy class flight tickets
2nd class train tickets
public transportation (no taxi fares)
hotel/accomdation charges up to the tax-expendable amount as listed at https://www.bundesfinanzministerium.de/Content/DE/Downloads/BMFSchreiben/Steuerarten/Lohnsteuer/2017-11-08-steuerliche-behandlung-reisekosten-reisekostenverguetungen-2018.pdf?_blob=publicationFile&v=2