In my opinion 1 1/2 month of bounty is not enough to get the potential people and their attention for this very potential bitcoin fork, I hope the BTC2 team will go to a deep study how this project will introduce in the masses.
i guess the dev don't want to spend much on bounty that is why the limited time for campaign, this project is not very know by many, i don't know maybe the devs have other marketing strategy in mind other than just bounty campaign to raise awareness,
also i think the payment is not very attractive to most bounty hunters to join, but non the less, this project will be known when the time comes.