If you're looking for a free, non-trial version of OctaneRender for Cinema 4D R25, you might want to consider the following options:
: If you are using a Mac with Apple Silicon (M1 or later), OTOY offers Octane X Prime for free. It is a single-GPU limited version that integrates with Cinema 4D (including R25) without watermarks. download octane render for cinema 4d r25 free
or specific "Prime" tiers depending on your hardware and software setup. Free Access Options OctaneRender Demo If you're looking for a free, non-trial version