Is it a question or another offer?
Well to let people participate in your bounty program first make your project and team convening enough, get ready with your project first and then go for marketing and bounty offerings.
Anyway I checked your bounty thread here some comments that might help you.
1. First what I see you are offering bounty program only for signatures and even this offer is very general.
You should categorize it for each Rank and member there should be different incentives for each for example
Category 1: Newbie - Jr. Member
Category 2: Member - Sr. Member
Category 3: Hero - Legendary
It should be more lucrative for higher level ranks only then they would signup. Specially getting the signatures of Hero and Legendary Members is not that easy. There are so many offers on the table for high ranker.
2. Sending an email to join and then one more google form. Why 2 steps?
Make it simple and single step, reply to the post and they are singed up. Or one google form should be enough.
And btw do you need post counts of the user?
3. Your own bounty program is not final.. how you expect people to join it?
Announce all your bounties once for all. Twitter, facebook, telegram or translation.
So it should sound that you are ready with your project and now you need marketing. See other examples in bounty programs.
Last but not the least there are many other things you should consider, you should invest first. Get your website translated to English too.
Hire a professional bounty manager. You can find penalty of experienced bounty mangers here on the forum it self try these boards
https://bitcointalk.org/index.php?board=52.0 and
https://bitcointalk.org/index.php?board=84.0Once you have bounty manager he/she will manage the bounties and running the campaign professionally. It is kind of full time job and requires time to followup and to encourage to people to join and spread the word.
Hope you won't take any comments to the hear.