I see that the 1.5 million USD State Department grant is listed on that return. I do hope that they weren't obligated to return that. The Award History section here [0] suggests that they were, but I don't know much at all about how these sorts of grants work.
Anyway. This is where Tor Project seems to officially publish their tax documents [1], but I can only find docs up to 2023->2024...
Notable is that in 2023->2024 (the year prior to the document you link to) Mullvad's funding was 1.4 million USD, whereas in 2024->2025, Mullvad's funding was 306 thousand USD. In that year, the Swedish International Development Cooperation Agency provided nearly twice the funding that Mullvad did! Perhaps Mullvad donated a enormously large amount of money in 2025->2026, but, yeah, the numbers don't support the "the Tor Project will start censoring because Mullvad is paying them so much" story.
Again, thanks for digging up that tax return.
[0] <https://www.usaspending.gov/award/ASST_NON_2534285_049#award...>