Figment is also free on GOG for the next 3 days:

https://www.gog.com/en/game/figment

I agree. Anyone is free to code whatever they like! If you feel like taking on a coding snack request that has already been answered, then go for it! Similarly, anyone is free to donate to anyone else for whatever reason they like, including donations for "duplicate" coding snacks.

The only point of clarification I would add is that if someone has posted a bounty/reward when requesting a coding snack, I wouldn't expect to claim the reward from the original requester if someone else has already answered the call and provided a solution. At least not without their pre-approval.