Gentoo is moving the non-technical organization overhead to Software in the Public Interest (SPI). As noted above, SPI is already now recognized at US federal level as a full-fleged non-profit 501©(3). It also handles several projects of similar type and size (e.g., Arch and Debian) and as such has exactly the experience and background that Gentoo needs. What are the advantages of becoming an SPI Associated Project in detail?

Financial benefits to donors:

tax deductions [1]

Financial benefits to Gentoo:

matching fund programs [2]
reduced organizational complexity
reduced administration costs [3]
reduced taxes [4]
reduced fees [5]
increased access to non-profit-only sponsorship [6]

Non-financial benefits to Gentoo:

reduced organizational complexity, no “double-headed beast” any more
less non-technical work required

[1] Presently, almost no donations to the Gentoo Foundation provide a tax benefit for donors anywhere in the world. Becoming a SPI Associated Project enables tax benefits for donors located in the USA. Some other countries do recognize donations made to non-profits in other jurisdictions and provide similar tax credits.

[2] This also depends on jurisdictions and local tax laws of the donor, and is often tied to tax deductions.

[3] The Gentoo Foundation currently pays $1500/year in tax preparation costs.

[4] In recent fiscal years, through careful budgetary planning on the part of the Treasurer and advice of tax professionals, the Gentoo Foundation has used depreciation expenses to offset taxes owing; however, this is not a sustainable strategy.

[5] Non-profits are eligible for reduced fees, e.g., of Paypal (savings of 0.9-1.29% per donation) and other services.

[6] Some sponsorship programs are only available to verified 501©(3) organizations

You can still donate to the SIP and the Förderverein in Germany.

Tldr gentoo isnt fedirally a non profit only in new mexico. Gentoo is going to have SPI do the finace for them and SPI is a nonprofit that runs debians and arch linux already so gentoo will be taxed less