Maybe something like this
1) maintainer creates a GitHub issue
2) public key created by maintainer for that issue
3) dev who wants to work on issue "claims" the issue and generates a new key, issue key + dev key (like a multi sig key)
4) cashu-address created from new key to solicit funds to do the work
5) dev does work and merges issue
6) maintainer reveals SK to dev to claim the cashu tokens. 

 Essentially the dev would wait for tokens to accrue before doing work. 
People contributing ecash can revoke the tokens at any time (e.g. maybe another dev comes along who will do it faster)

"Defunct" Tokens will never be claimed unless maintainer + dev collude and the tokens aren't revoked