At https://downloads.openwrt.com - on the same page that you find the image for your router.
At the bottom of the page, there's a download for your relevant Software Development Kit (SDK). Everything is included in the SDK.
The SDKs are made to work on Linux x86_64. The only method is to cross compile. The OpenWrt Wiki has a cross-compile page. All linked on the AMPR Wiki page.
-------- Original message --------
From: Harold via 44net <44net@mailman.ampr.org>
Date: 1/27/23 02:37 (GMT-05:00)
To: 44net@mailman.ampr.org
Subject: [44net] ampr-ripd 2.4.1 / openwrt
Ok I know there are A LOT of post from the PAST about compiling ampr-ripd for OpenWRT but for the last few days, I have been racking my brain trying