While it's not an exact match, patreon.com more or less does this in letting people crowdsource one-time/monthly payments to a person in exchange for their works. I know several musicians, youtubers, and social media personalities that have used it to varying degrees of success.
I wish there was an easy way to crowdfund maintained releases. I've been burned by 3 frameworks moving on with no backwards-compatibility; that was worth money to myself & my business to keep them maintained.
Unfortunately, not enough to hire someone full-time or coordinate it (the original developers in all cases had no interest).
Does this exist?