In June 2024 Robert Edgar donated binaries for versions 5 through 11 of USEARCH to the public domain. You can now download them for free, including the 64-bit versions that used to cost $1,500, from this GitHub repository. At the same time USEARCH version 12 was launched as an open-source project at https://github.com/rcedgar/usearch12. See this paper announcing the open-source project.
Reference
Zhou Y, Liu YX, Li X. 2024. USEARCH 12: Open-source software for sequencing analysis in bioinformatics and microbiome. Imeta 3:e236.