You should be more open with your budget . “Compensation based on international market rates” isn’t something that will attract a senior java dev unless he is desperate. According to google the pay should be no less than $10k/month btw.
Good luck with bisq2 I hope it kills all the centralized exchanges.
Payment depends on qualification. Up to 16 000 USD is not unusual for Bisq developers.
See past contribution requests:
https://github.com/bisq-network/compensation/issues?q=is%3Aissue%20state%3Aclosed