Earlier quoted context omitted.
We are not talking about hundreds or thousands of dollars here, are we? Do you get in trouble with the Tax Man because you tip your server at a restaurant or gives some spare change to the someone on the street?
Giving? No. Receiving and not reporting? Maybe, depending on local laws and how zealous the tax enforcer is. This probably falls into the category of "Not allowed, but too small to worry about." That works fine, until they decide to audit you for some other reason.
Sure, if the project is successful to the point of receiving significant amounts, having to report it becomes mandatory.
Speaking as someone with an open source project that started due a grant and that I'd love to turn into a full time job: If I were receiving so many donations that it would require me to spend time to report to the tax authorities, I'd put it on the list of "good problems to have".