OpenBSD is not going to become a charity because of the overhead to the accounting involved. I understand that.
In that case, OpenBSD should not ask for donations from business since it can not give a tax receipt, and further more if OpenBSD could give a charitable tax receipt that tax receipt probably not be good in any other country than Canada. Instead OpenBSD should ask for advertising money. Advertising is a valid expense for every company in every country. For the company's money, OpenBSD could give either banner add or just a page listing advertisers. In some cases countries only allow advertising money to be spend where the paying country does business. In that case, the money could be using to finance a ftp or web server in that country.