Has the OpenBSD Foundation looked into registering with the IRS as a 501(c)(3) organization? The IRS probably has 10-12x more tax payers than the CRA which would make it easier to cover the required overhead.

It looks like the requirements are a $275 application fee, an EIN (so the Foundation would need to apply for one), and an annual information return. No need to incorporate or form a separate US entity.