You can create that and I think in 99% percent of cases you can also collect github donations without problems in Finland. If it were to go in court I think it could be easily explained as non-donation because there is work performed.
Also OPs explanation is not so straightforward, the money collection act is being contested all the time and many succeed in collecting money here.
Basically you state that it isnt donation but payment for gig. Which would apply to github "donations" as well, they arent donations but payment for the open source work.
Finnish peoples problem isnt the laws, but the fact that they are total pussies when it comes intrepreting the law.
Sure if you set up your sponsor tiers like "$5/mo: x minutes of bugfixing for you" then it would be just sales. I think if you just accept money and say "thanks" in return with a vague promise of working on open source, that's a pretty grey area and I'd rather not have to explain it to the authorities in the first place. :P
