Development is never free, but this seems to be driven by a P2P protocol so hosting/bandwidth costs should be close to zero (maybe signalling server is hosted by creator but should be relatively cheap to host). I agree that donation would be nice, but won't prevent it from disappearing. Only solution I can think of to completely make it unable to disappear would be to open source the code base, either now or having a guarantee that the code base would be open sourced if the author looses interest.