https://www.sidefx.com/community/production-build-update-165378/
The Houdini Indie program has been a successful initiative designed to provide indie animators and gamedevs, who have a gross income less than $100K USD, with access to the features of Houdini FX with very few restrictions.
In response to feedback from the Houdini Indie community, SideFX is increasing the render resolution limit for image sequences from 1080p to 4K x 4K in order to facilitate the generation of high definition imagery, which is especially important for artists creating VR content.
[...]With these added features and the recent addition of third party rendering, SideFX has set a new annual price for Houdini Indie of $269 USD for a single year or $399 USD for a two-year term.