1. Adblock Plus is fully open source, has always been, will always be. Everything else we do is open source too, including our infrastructure and backend systems. (https://hg.adblockplus.org/)
2. Adblock Edge is an unmaintained (edit: Not true, there've been some changes lately) fork of an old Adblock Plus version, with the Acceptable Ads feature removed.
3. Acceptable Ads are an opt-out feature which whitelists ads that comply with the Acceptable Ads criteria. Large sites have to support the project in return, but there's no way around the criteria. (https://adblockplus.org/en/about)
As an aside, we're currently looking into a way of making it easy for users to whitelist ads on YouTube channels they like automatically. Pre-roll video ads will never be acceptable and hence never will be whitelisted for all users by default, but many people still want to support individual YouTubers.