here's what i can tell so far, i think.
1) r4i-sdhc.com team is the creator of the R4IMenu firmware. they've used it since day one. They have had time bombs, but there's a special timebomb disabled "final firmware" for ONE of their older carts.
2)r4isdhc.com has used many firmwares,and i'm pretty sure none of them are their own. sometimes back in 2013 they started cloning r4i-sdhc.com carts, because they had an actively developed firmware. These are imperfect clones, which is why retrgamefan ysmenu has issues with DSI enhanced games on them. Their older carts used a different firmware, and expect to find ds_menu.dat on the sdcard. they run variants of wood,r4itt, and who knows WHAT else. many cart teams took the open source RPG firmware and modified it. but it looks like this team has never made an original firmware in it's life, even going straight fro the source.
3) r4isdhc.com.cn seems to be also using wood and akmenu/akaio variants, with all CN cards accepting a hacked wood 1.62. every singe download page offers the same hacked wood, so all their clones seem to use the same encyption key. I suspect that they just took ace3ds hacked wood and changed it's name a bit to make their current firmware.