Since Firefox OS is discontinued and lots of files on its CDN is removed, I upload my backups and hope that can help those who need it.
v18D_nightly_v4.zip SHA512 = 9105e29fd39da1ae487b01da4431a803d619d31482147b4383002b8a10268905fd444b108a438395a78d289cfe4e8fba10c3fb6b0d187f3535f027bf90c2391a https://drive.google.com/file/d/0B0LIhpR4sgJrUlhOdTZ1Z2V6R2c/view
From: https://developer.mozilla.org/en-US/docs/Archive/B2G_OS/Phone_guide/Flame/Updating_your_Flame