Qubes offers great protection of your privacy. First, since everything is compartmentalized. a compromised browser/PDF reader etc will not give the attacker access to the rest of your system and sensitive files.
Secondly, the networking system and ProxyVM's make it very easy to route your(or part of your) traffic through VPN/Tor, and if the VM is compromised, it cannot obtain your real IP address since all its traffic is routed through the ProxyVM.
Mullvad has already donated to Qubes OS.
They have a decentralized bitcoin fund (https://www.qubes-os.org/news/2016/07/13/qubes-distributed-fund/) and are also on Open Collective(https://opencollective.com/qubes-os) which offers great transparency and pays the individual developers directly.